Ultrafast Surface Dynamics 6 Kloster Banz, Germany - Max-Born ...

Ultrafast Surface Dynamics 6
July 20–25, 2008
Kloster Banz, Germany

WELCOME
Foreword
to the 6th conference on Ultrafast Surface Dynamics. It is by now a tradition that our meeting
takes place at a hard to reach and thus hard to leave location. This time it is the former monastery
Kloster Banz in the heart of Franconia. We wish you a pleasant stay in this rather unknown but
beautiful part of Germany. We hope that you enjoy the scientific program of USD 6 and we are
looking forward to stimulating talks and discussions.
HISTORY
Martin Weinelt, Uwe Bovensiepen, and Thomas Fauster
Ultrafast Surface Dynamics is a biannual international conference and the main place for informal,
scientific exchange in the field of ultrafast dynamics at surfaces and interfaces. Previous
meetings were held at
• Ascona (Switzerland 1997)
• Ringberg (Germany 1999)
• San Sebastian (Spain 2001)
• Telluride (USA 2003)
• Abashiri (Japan 2006)
SCOPE
The electronic, magnetic, and optical properties of solids are determined by the dynamic response
of their carriers to internal and external fields. We know most of the equilibrium properties of
solids from measurements of the thermal, electrical, and optical conductivity. Non-equilibrium
properties are in contrast much harder accessible. They comprise carrier-carrier scattering and
quasiparticle formation on a picosecond to attosecond time scale. Collective excitations as well
as quasielastic and inelastic scattering processes of individual charge carriers lead, e. g., to the
formation of phonons, plasmons, excitons, polarons, or magnons. Ultrafast dynamics at surfaces
includes in addition the transport of charge and energy through interfaces and the concomitant
relaxation processes. The latter determine carrier recombination at semiconductor interfaces,
photo-induced diffusion, desorption and reactions of adsorbates, charge transfer in nanostructures,
at membranes, and in molecular films, switching of molecules at surfaces, solvation in polar
media and at their surfaces, as well as spin- and magnetization dynamics in magnetic multilayers.
In the last years we witnessed ground-breaking time-resolved experiments, which became feasible
by the rapid progress in femtosecond laser technology such as phase stabilization, pulse
compression in fibers, and adaptive control of ultrashort laser pulses. These experimental developments
go hand in hand with increasingly extensive many-body theory calculations of the
self-energy, studies of wave-propagation for electrical fields or quasiparticles, and the development
of the time-dependent density functional theory.
i

Foreword
PROGRAM
We have grouped the recent progress in the field of Ultrafast Surface Dynamics into the following
topics which are represented by distinguished invited speakers:
• Attosecond physics and ultrafast X-ray pulses
Ferenc Krausz, Margaret Murnane, and Wilfried Wurth
• Correlated materials
Dan Dessau, Alfred Leitenstorfer, Luca Perfetti and Kurt Schönhammer
• Electron dynamics and electronic energy transfer at surfaces
Pedro M. Echenique, Jean-Pierre Gauyacq, Charles B. Harris, Tony F. Heinz, Tobias Hertel,
Eckhard Pehlke, and Katsumi Tanimura
• Laser-induced reactions of adsorbates and dynamics in molecular films
Ulrich Höfer, Karina Morgenstern, Martin Wolf, and Xiaoyang Zhu
• Spin-dependent dynamics and ultrafast magnetization
Martin Aeschlimann, Douglas L. Mills (cancel.), Theo Rasing (cancel.), and Joachim Stöhr
• Ultrafast microscopy and coherent control
Dwayne Miller, Hrvoje Petek, Walter Pfeiffer, and Tamar Seideman
• Vibrational energy transfer and wave-packet dynamics
Mischa Bonn and Yoshiyasu Matsumoto
PROMOTING YOUNG RESEARCHERS
Based on the quality of the submitted abstracts the program committee upgraded the contributions
of Ryuichi Arafune, Anca-Monia Constantinescu, Alexey Melnikov, Markus B. Raschke,
Anke B. Schmidt, and Aimo Winkelmann to extended talks.
FINANCIAL SUPPORT
We are grateful to the Deutsche Forschungsgemeinschaft (DFG) as the main source of financial
support. We thank the Wilhelm und Else Heraeus-Stiftung for travel grants for students who
are members of the German Physical Society (DPG). The Max Born Institute has approved a
significant amount of overhead. Poster sessions and conference outing are cosponsored by the
companies SPECS, Coherent, Newport/Spectra-Physics, Femtolasers, Horiba Jobin Yvon, and
Wiley-VCH.
INTERNATIONAL STEERING COMMITTEE
Pedro M. Echenique, Tony F. Heinz, Ulrich Höfer, Yoshiyasu Matsumoto, Hrvoje Petek, Martin
Wolf, and Xiaoyang Zhu
CHAIRPERSONS AND LOCAL ORGANIZERS
Martin Weinelt, Uwe Bovensiepen, and Thomas Fauster
CONTACT
Martin Weinelt
Max-Born-Institut
Max-Born-Strasse 2A
12489 Berlin, Germany
Phone: +49-30-6392 1210
Fax: +49-30-6392 1209
Email: weinelt@mbi-berlin.de
Local address
Bildungszentrum Kloster Banz
96231 Bad Staffelstein
Germany
Phone: +49-9573-3370
Fax: +49-9573-33733
Email: banz@hss.de
ii

Program overview
Sunday 16:50
Opening session . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Monday 9:00
Electron dynamics and electronic energy transfer at surfaces 1 . . . . . . . . . . . . . . . . . . . . . . . . . 7
Monday 14:40
Electron dynamics and electronic energy transfer at surfaces 2 . . . . . . . . . . . . . . . . . . . . . . . . 14
Monday 19:30
Poster session . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Tuesday 9:00
Spin-dependent dynamics and ultrafast magnetization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
Wednesday 9:00
Attosecond physics and ultrafast X-ray pulses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
Wednesday 14:40
Vibrational energy transfer and wave-packet dynamics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
Wednesday 19:30
Poster session . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
Thursday 9:00
Correlated materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
Thursday 14:40
Ultrafast microscopy and coherent control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88
Author index. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .96
Post-deadline contributions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100
1

Timetable
9:00
9:20
9:40
10:00
10:20
10:40
11:00
11:20
11:40
12:00
12:20
12:40
13:00
13:20
13:40
14:00
14:20
14:40
15:00
15:20
15:40
16:00
16:20
16:40
17:00
17:20
17:40
18:00
18:20
18:40
19:30
22:00
Sunday Monday Tuesday Wednesday Thursday
Registration
Coffee & cake
16:50 Welcome
M. Wolf
K. Morgenstern
T. F. Heinz
Welcome BBQ
P. M. Echenique
C. B. Harris
Coffee break
K. Yamashita
J.-P. Gauyacq
U. Höfer
T. Ichibayashi
13:20 Lunch
E. Pehlke
K. Tanimura
X. Y. Zhu
Coffee break
T. Hertel
R. Arafune
A. Winkelmann
Poster session
J. Stöhr
M. Aeschlimann
Coffee break
H. A. Dürr
A. Melnikov
A. B. Schmidt
12:30 Lunch
13:30 Bus depart.
Excursion
to Bamberg
F. Krausz
W. Wurth
Coffee break
B. Abel
M. Murnane
S. Mathias
L. Miaja-Avila
M. Bauer
13:20 Lunch
Y. Matsumoto
C. Frischkorn
R. Frigge
K. Ishioka
M. Hase
Coffee break
M. B. Raschke
Constantinescu
M. Bonn
Poster session
Electron dynamics and electronic energy transfer at surfaces
Spin-dependent dynamics and ultrafast magnetization
Attosecond physics and ultrafast X-ray pulses
Correlated materials
Laser-induced reactions of adsorbates and dynamics in molecular films
Vibrational energy transfer and wave-packet dynamics
Ultrafast microscopy and coherent control
2
A. Leitenstorfer
K. Schönhammer
Coffee break
P. S. Kirchmann
L. Perfetti
B. Gumhalter
D. Dessau
13:20 Lunch
R. J. D. Miller
A. Hanisch
W. Pfeiffer
N. M. Buckanie
Coffee break
T. Munakata
T. Seideman
H. Petek
Conference dinner

Opening session
15:00 Registration
16:00 Coffee & cake
16:50 Welcome
Sunday afternoon
17:00 Ultrafast dynamics of electron transfer and solvation processes at polar adsorbate/metal
interfaces
Martin Wolf
17:40 Dynamics and Function in Molecular Layers
Karina Morgenstern
18:20 Fundamental Excitations and Their Dynamics in Carbon Nanotubes and Graphene
Tony F. Heinz
19:00 Break
19:30 Welcome reception & BBQ
3

Electronic energy transfer
Invited talk Sunday 17:00
Ultrafast dynamics of electron transfer and solvation processes at polar
adsorbate/metal interfaces
MARTIN WOLF
Department of Physics, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
wolf@physik.fu-berlin.de
Electron transfer (ET) across interfaces is of vital importance in different areas of physics, chemistry
and biology. In the last few years we have studied the dynamics of interfacial electron
transfer and solvation processes in ice and ammonia layers adsorbed on single crystal metal
surfaces by time-resolved two-photon-photoemission (2PPE) spectroscopy [1]. In this process,
photoinjection of electrons from the metal into the adsorbate conduction band is followed by ultrafast
localization and solvation of the excess electrons. The subsequent energetic stabilization
of these solvated electrons due to nuclear rearrangements of the polar molecular environment is
accompanied by an increasing degree of localization.
Fig. 1 a) 2PPE scheme indicating
the subsequent population
of a precursor state eP and solvated
electron state eS in NH3 on
Cu(111). b) Time-resolved 2PPE
spectra of a 17 ˚A thick amorphous
NH3 film on Cu(111). The
dominant peak is attributed to
solvated electrons at the ammonia/vacuum
interface.
Here we focus on the electron dynamics in amorphous NH3 adlayers on Cu(111) (see Fig. 1):
Two different species of interfacial electrons are observed, (i) a precursor state (eP) exhibiting
fs transfer times and solvation dynamics and (ii) a solvated electron state (eS), which envolves
on a 1–100 ps timescale. We find that the electron transfer rate of eS back to the Cu substrate
depends exponentially on NH3 layer thickness, allowing the extraction of the transient tunnelling
barrier at different stages of solvation. Thus, NH3/Cu(111) provides a nice model system to
demonstrate various phenomena of interfacial ET, like thermally activated tunnelling, which has
not be observed for D2O layers due to stronger electronic coupling.
Acknowledgement: This work was performed in collaboration with M. Bertin, U. Bovensiepen, C. Gahl,
D. Kusmierek, M. Meyer, J. Stähler (FU Berlin), M. Mehlhorn, K. Morgenstern (U Hannover) and X. Y.
Zhu (U Minnesota)
[1] J. Stähler, U. Bovensiepen, M. Meyer, and M. Wolf, A Surface Science Approach to Ultrafast Electron
Transfer and Solvation Dynamics at Interfaces, Chem. Soc. Reviews (submitted)
4

Vibrational energy transfer
Invited talk Sunday 17:40
Dynamics and Function in Molecular Layers
KARINA MORGENSTERN
Institute for Solid State Physics, Leibniz University of Hannover, Germany
morgenstern@fkp.uni-hannover.de
The tip of a scanning tunnelling microscope (STM) can be viewed as a highly localized electron
beam, whose energy can be tuned by the applied voltage. The inelastic part of this electron beam
might excite vibrations of surfaces or of adsorbed molecules. By this, it is possible to measure
vibrations and to induce chemical reactions. Implementation of this method demands imaging at
low temperature (5K) with submolecular resolution, in order to identify molecular side groups
and position the tip exactly above a specific part of the molecule. In this talk, I will present
vibrational spectra of individual water molecules adsorbed on Au(111) and the pure Au(111)
surface. The reaction is exemplified on the rearrangement of hydrogen bonds within ice clusters
and crystalline ice layers. The energy dependence of the induced reactions allows determination
of the excitation mechanism. Femtosecond laser pulses are a second means to produce high
energetic electrons close to adsorbed molecules. The combination of a femtosecond laser with a
STM allows investigating reactions locally. This will be demonstrated for CO/Cu(111).
5

Advances in ultrafast surface spectroscopies
Invited talk Sunday 18:20
Fundamental Excitations and Their Dynamics in Carbon Nanotubes and
Graphene
TONY F. HEINZ
Departments of Physics and Electrical Engineering, Columbia University, New York, USA
tony.heinz@columbia.edu
Carbon nanotubes and graphene represent the one- and two-dimensional forms of sp 2 -hybridized
carbon in which every atom is at the surface. Both materials have unusual mechanical properties
associated with the strong bonding of light atoms. Perhaps even more distinctive are the
electronic excitations and charge transport properties of these materials. In this paper, we will
review current understanding of optical excitations in carbon nanotubes and graphene. Recent
experimental advances have permitted direct characterization of electronic transitions in both
individual nanotubes and well-defined graphene monolayers. We will demonstrate how the electronic
states in these monolayer-thick materials can be modified by the external environment
through the application of strain and modification of the surrounding dielectric environment. We
will also present results on the ultrafast relaxation dynamics of electronic excitations in these
systems and the coupling of these excitations to phonons.
6

Electron dynamics and electronic energy transfer at surfaces 1
9:00 A novel low-energy collective electronic excitation at metal surfaces
Pedro M. Echenique
9:40 Ultrafast Electron Dynamics at Interfaces
Charles B. Harris
10:20 Coffee break
Monday morning
11:00 Model Eliashberg Function Based Study of Electron-Phonon Coupling in Cs/Cu(111)
Akihiro Nojima, Koichi Yamashita, Bo Hellsing
11:20 Electron propagation along Cu atomic wires supported on a Cu(111) surface
Jean-Pierre Gauyacq, Sergio Díaz-Tendero, Fredrik E. Olsson, Andrei G. Borisov
12:00 Electron Dynamics at the Interface between an Organic Semiconductor and a Metal
Christian Schwalb, Manuel Marks, Sönke Sachs, Achim Schöll, Friedel Reinert, Eberhard
Umbach, Ulrich Höfer
12:40 Hot-hole and hot-electron dynamics at Si surfaces studied by time-resolved twophoton
photoemission spectroscopy
Taku Ichibayashi, Katsumi Tanimura
13:00 Break
13:20 Lunch
7

Electronic energy transfer
Invited talk Monday 9:00
A novel low-energy collective electronic excitation at metal surfaces
PEDRO M. ECHENIQUE
Departamento de Física de Materiales, and Centro Mixto UPV/CSIC, and Donostia
International Physics Center (DIPC), 20018 San Sebastian/Donostia, Basque Country, Spain
pedromiguel.echenique@ehu.es
We show that, in contrast to earlier expectations, a low energy collective excitation mode can
be found on bare metal surfaces. The mode has an acoustic (linear) dispersion, different to the
q 1/2 of a 2D plasmon, and was observed on Be(0001) using angle-resolved electron energy loss
spectroscopy. First-principles calculations show that it is caused by the coexistence of a partially
occupied quasi-2D surface-state band with the underlying 3D bulk electron continuum. This
plasmon has a very general character and should be present on many metal surfaces. Furthermore,
its acoustic dispersion allows the confinement of light on small surface areas and in a broad
frequency range, which is relevant for nano-optics and photonics applications.
8

Electronic energy transfer
Invited talk Monday 9:40
Ultrafast Electron Dynamics at Interfaces
CHARLES B. HARRIS
Department of Chemistry University of California Berkeley, CA 94720, USA
cbharris@berkeley.edu
We have employed angle-resolved two photon photoemission to investigate the dynamics of excited
state electrons in ultrathin, organic films on Ag(111) mimicking two vastly differing systems.
First, the low differential capacitance of the electrochemical solvent dimethylsulfoxide (DMSO)
was examined. Image potential state electrons are solvated by 50±10 meV and 220±10 meV for
the first and second monolayers, respectively. Because the first monolayer of DMSO is tethered
to the metal surface via multiple bonds, it is rotationally hindered from solvating excess charge,
supporting previously proposed mechanisms. The relationship between the image potential
states and interfacial capacitance is discussed. The second system studied was the evolution of
the surface band structure of an organic semiconductor in contact with a noble metal. The morphology
of the perylene based molecule PTCDA was controllably varied on the Ag(111) surface
by controlling the temperature of the substrate during molecular beam epitaxial dosing. Growth
modes ranged from highly crystalline Stranski-Krastanov style growth at high temperatures to
rotationally disordered layer-by-layer growth at cryogenic temperatures. Lifetimes for the differing
morphologies varied from tens of femtoseconds to several picoseconds. The band masses
and population of both the LUMO and IPS bands were measured. These measurements were then
used to directly connect interfacial charge mobilities to morphological properties of the ultrathin
films.
PTCDA
Ag(111)
Energy (eV)
9
0.45
0.43
0.41
melec
* = 0.5 m0
0 0.02 0.06 0.10
k|| (A-1)

Coherent phenomena
Talk Monday 11:00
Model Eliashberg Function Based Study of Electron-Phonon Coupling in
Cs/Cu(111)
AKIHIRO NOJIMA 1 , KOICHI YAMASHITA 1 , and BO HELLSING 2
1 Department of Chemical System Engineering, The University of Tokyo, Tokyo, Japan
2 Department of Physics, Göteborg University, Göteborg, Sweden
yamasita@chemsys.t.u-tokyo.ac.jp
A simplified calculation scheme is proposed for the analysis of the phonon-induced lifetime
broadening of surface electronic states. The aim has been to develop a scheme which is more
appropriate than simple Debye models but less cumbersome than first principles methods. This is
particular important when considering complex systems, such as overlayer systems. The scheme
presented for the calculation of the Eliashberg function includes the essential ingredients for the
electron-phonon coupling in terms of electron and phonon structure of the system. We apply this
procedure to the image and surface state of Cu(111) and to the quantum-well and newly found
Gap state of p(2x2)-Cs/Cu(111). We demonstrate that low frequency phonon modes localized to
the overlayer play a crucial role in the electron scattering process and for the lifetime of surface
localized electronic states.
[1] A. Nojima, K. Yamashita, and B. Hellsing, J. Phys.: Condens. Matter 20, 224017 (2008)
[2] A. Nojima, K. Yamashita, and B. Hellsing, Appl. Surf. Sci., available on line 9 April (2008)
10

Electronic energy transfer
Invited talk Monday 11:20
Electron propagation along Cu atomic wires supported on a Cu(111)
surface
JEAN-PIERRE GAUYACQ 1,2 , SERGIO DÍAZ-TENDERO 1,2 , FREDRIK E. OLSSON 3 , and
ANDREI G. BORISOV 1,2
1 CNRS, Laboratoire des Collisions Atomiques et Moléculaires, UMR 8625,
Bâtiment 351, 91405 Orsay Cedex, France
2 Université Paris-Sud, Laboratoire des Collisions Atomiques et Moléculaires, UMR 8625,
Bâtiment 351, 91405 Orsay Cedex, France
3 Department of Applied Physics, Chalmers/Göteborg University,
S-41296 Göteborg, Sweden
jean-pierre.gauyacq@u-psud.fr
Electronic states localized on atomic chains supported on metal surfaces have been observed in
several systems [1,2]. Detailed analysis of their energies have been reported but up to now their
lifetime has not been investigated, despite its central importance in a discussion of the existence
of these states. We studied the 1D-sp band localized on an infinite Cu atomic chain supported on a
Cu(111) surface using a theoretical approach based on both DFT (Density Functional approach)
and WPP (Wave Packet Propagation)[3]. We determined the dispersion relation of the band and
most importantly the lifetime of the states localized on the chain.Our results are in quantitative
agreement with the STM experimental data of S.Fölsch et al[2], once the perturbing action of the
STM field has been taken into account.
The calculations show a partial decoupling of the chain-localized states from the metal substrate,
allowing a finite lifetime for the electrons propagating along the atomic chain. This is attributed
to the effect of the Cu(111) surface-projected band gap that partially blocks the resonant electron
transfer from the wire to the substrate. We also determine the distance travelled by an electron
along the chain before escaping into the Cu substrate. It is of the order of five Cu-Cu interactomic
distances. As a consequence, atomic chains on Cu(111) can be considered as short nanowires
able to guide an electron flux along a short distance. The possibility of significantly increasing
the distance travelled by excited electrons along a wire for certain nanowire systems will also be
addressed.
[1] N. Nilius, T. M. Wallis, and W. Ho, Science 297, 1853 (2002)
[2] S. Fölsch, P. Hyldgaard, R. Koch, and K. H. Ploog, Phys. Rev. Lett. 92, 056803 (2004)
[3] F. E. Olsson, M. Persson, A. G. Borisov, J. P. Gauyacq, J. Lagoute, and S. Fölsch, Phys. Rev. Lett. 93,
206803 (2004)
11

Electronic energy transfer
Invited talk Monday 12:00
Electron Dynamics at the Interface between an Organic Semiconductor
and a Metal
CHRISTIAN SCHWALB 1 , MANUEL MARKS 1 , SÖNKE SACHS 2 , ACHIM SCHÖLL 2 , FRIEDEL
REINERT 2 , EBERHARD UMBACH 2,3 , and ULRICH HÖFER 1
1 Fachbereich Physik, Philipps-Universität Marburg, D-35032 Marburg, Germany
2 Universität Würzburg, Experimentelle Physik II, D-97074 Würzburg, Germany
3 Forschungszentrum Karlsruhe, D-76021 Karlsruhe, Germany
hoefer@physik.uni-marburg.de
Ultrafast surface spectroscopies can provide detailed information about the microscopic mechanisms
of electron transfer processes at interfaces between organic semiconductors and metals.
In this talk, we report about a recent study of 3,4,9,10-perylene tetracarboxylic acid dianhydride
(PTCDA) grown epitaxially on Ag(111). Two-photon photoemission (2PPE) displays a unoccupied
dispersing state between the metallic Fermi level and the lowest unoccupied molecular
orbitals (LUMO) of PTCDA. Its energetic position in the band gaps of both the Ag(111) substrate
and the PTCDA overlayer identify it as a genuine interface state, a result that is corroborated
by model calculations. The lifetime of electrons excited into this interface state is 55 fs. This is
a relatively small value for an unoccupied state located only 0.6 eV above the Fermi level. It is
indicative for a large penetration of the wavefunction into the projected sp-gap of Ag(111). In
order to investigate the role of the interface state for carrier transport between the organic semiconductor
and the metal we populate the LUMO of PTCDA by absorbing 2.4 eV photons in films
of varying thickness up to 100 ML and simultaneously record fluorescence and angle-resolved
photoemission spectra. We observe a long lived component in the 2PPE intensity close to the
Fermi level which clearly correlates with film thickness and fluorescence lifetime.
12

Electronic energy transfer
Talk Monday 12:40
Hot-hole and hot-electron dynamics at Si surfaces studied by time-resolved
twophoton photoemission spectroscopy
TAKU ICHIBAYASHI and KATSUMI TANIMURA
The Institute of Scientific and Industrial Research, Osaka University, Osaka, Japan
ichbys35@sanken.osaka-u.ac.jp
Several striking effects, like non-thermal melting, photoinduced phase transformation, electronic
ablation etc, induced by ultrashort laser interaction with solids have emphasized comprehensive
understanding of ultrafast carrier relaxation in fs-time regime to elucidate the mechanism
involved. Here we use time-resolved two-photon photoelectron spectroscopy (2PPE) to reveal
characteristic features of ultrafast relaxation of photogenerated hot-holes and hot-electrons for
Si. Well characterized Si(111)-(7x7) and Si(001)-(2x1) surfaces were pumped by 100-fs laser
pulses with photon energies (hν) in visible region, generated by an optical parametric generator,
and the photoemission was probed by the third (3ω) or the forth harmonics (4ω) of a Ti-sapphire
laser. The 3ω is used for studying hot-electron dynamics exclusively, while the 4ω for hot-hole
dynamics.
For pump-photon energies below 2.5 eV, the intra-valley scattering leads to the quasi-equilibrated
electronic system, characterized by an effective temperature T ∗ typically 2000 K, near the
conduction-band minimum (CBM) within 150 fs after excitation. T ∗ increases with hν and a
half of the excess energy is conserved within the electronic system during the process. The hot
electronic system is then cooled down via electron-phonon interaction with a common energyrelaxation
time of 240 fs, irrespective of hν. During the cooling process, a substantial fraction of
electrons is reduced within 1 ps for both surfaces. The hot-hole signal, detected by a reduction of
photoemission intensities probed by 4ω, shows a similar ultrafast reduction. For Si(111)-(7x7)
surfaces, the pump-pulse induced reduction in intensity of the S2 rest-atom band at 0.8 eV below
S1/U1 band, shows an ultrafast recovery (annihilation of holes) within 1 ps, followed by a
gradual one lasting over several tens of ps. Time- and angle-resolved measurements on the hothole
dynamics shows an interesting hole-transfer dynamics between bulk-valence band and the
surface-specific electronic bands for both Si(111)-(7x7) and Si(001)-(2x1).
13

Monday afternoon
Electron dynamics and electronic energy transfer at surfaces 2
14:40 TDDFT molecular-dynamics simulation of electronically non-adiabatic processes at surfaces
Jan van Heys, Henning Husser, Michael Lindenblatt, Eckhard Pehlke
15:20 Ultrafast carrier dynamics on Si surfaces studied by time-resolved twophoton photoemission
spectroscopy
Katsumi Tanimura
16:00 Spectroscopic probe of polaron and exciton dynamics in organic semiconductors
Matthias Muntwiler, Qingxin Yang, William Tisdale, Xiaoyang Zhu
16:40 Coffee break
17:20 Exciton localization, decay and diffusion in carbon nanotubes and nanotube crystallites
Tobias Hertel
18:00 Energy gain process in laser photoemission through excitation of surface vibrations
Ryuichi Arafune, Mayuko Yamamoto, Noriaki Takagi, Yoichi Uehara, Sukekatsu Ushioda,
Maki Kawai
18:30 Interferometric control of spin-polarized three-photon photoemission from Cu(001)
Aimo Winkelmann, Wen-Chin Lin, Francesco Bisio, Hrvoje Petek, Jürgen Kirschner
19:00 Beer and Snacks
19:30 Poster session
14

Electronic energy transfer
Invited talk Monday 14:40
TDDFT molecular-dynamics simulation of electronically non-adiabatic
processes at surfaces
JAN VAN HEYS, HENNING HUSSER, MICHAEL LINDENBLATT, and ECKHARD PEHLKE
Institut für Theoretische Physik und Astrophysik, Universität Kiel, 24098 Kiel, Germany
pehlke@theo-physik.uni-kiel.de
The mechanisms of energy-transfer dynamics between electronic and vibrational degrees of freedom
at surfaces is of considerable interest. For example, during exothermic reactions of atoms or
molecules with metal surfaces part of the chemisorption energy my be spent to excite electronhole
pairs in the metal. This electronic dissipation channel occurs concurrently to energy dissipation
directly into phonons. Mizielinski et al. [1] have modelled the electron-hole pair-excitation
process by means of a time-dependent Newns-Anderson model. They have pointed out that during
adsorption the dynamics may deviate strongly from the Born-Oppenheimer surface, and the
nearly adiabatic approximation fails. As electronic excitation effects are expected to be most
pronounced for a light, and thus fast, atom interacting with a metal surface, we have chosen to
simulate the chemisorption of hydrogen atoms on the Al(111) surface. To this purpose we apply
a combination of spin-polarized time-dependent density-functional theory for the electrons and
Ehrenfest dynamics for the nuclei. The chemisorption process is simulated over up to 70-80 fs for
cells containing up to 500 electrons. While such simulations are extremely costly, they provide
the opportunity to avoid (and validate) assumptions that have to be invoced in model calculations.
The energy transferred into electron-hole pair excitations, the excitation spectra, and the
nonadiabatic contribution to the force is calculated [2].
The second example for energy-transfer processes at surfaces pertains to the excitation of coherent
surface atomic motion by intense fs laser pulses. Coherent phonon excitation is well known
for bulk phonons. Due to the strong Jahn-Teller like coupling between the electronic structure
of the Si(001) dangling bonds and the buckling angle of the Si-dimers, the Si(001) surface constitutes
an excellent candidate to investigate coherent surface vibrational excitation. TDDFTsimulations
for intense fs laser pulses with a photon energy ∼1.7 eV (value optimized for DFT)
and a width at half maximum of ∼ 12 fs have been carried through. The dimer buckling angle
reacts to the potential-energy change induced by the strong electronic excitation on a typical
timescale of the order of 100 fs [3]. The response is not monotonic with respect to laser intensity.
Finally we will discuss future prospects for the TDDFT-molecular dynamics simulations approach,
e.g. for the direct simulation of photo-emission currents induced by fs laser pulses.
[1] M. S. Mizielinski, D. M. Bird, M. Persson, and S. Holloway, J. Chem. Phys. 122, 084710 (2005)
[2] M. Lindenblatt and E. Pehlke, Phys. Rev. Lett. 97, 216101 (2006)
[3] J. van Heys, M. Lindenblatt, and E. Pehlke, Phase Transitions 78, 773 (2005)
15

Electronic energy transfer
Invited talk Monday 15:20
Ultrafast carrier dynamics on Si surfaces studied by time-resolved
twophoton photoemission spectroscopy
KATSUMI TANIMURA
The Institute of Scientific and Industrial Research, Osaka University Mihogaoka 8-1, Ibaraki,
Osaka 567-0047, Japan
Tanimura@sanken.osaka-u.ac.jp
Carrier dynamics on semiconductor surfaces is of great scientific and technological interest. In
combination with carrier diffusion and drift transport, ultrafast primary processes of carriercarrier
(e-e) scattering and electron-phonon (e-p) scattering in bulk electronic states, govern the
dynamics near surfaces. In spite of the accumulating knowledge, no direct picture of the carrier
relaxation in bulk states nor of dynamical coupling of bulk electrons to intrinsic Si surface states
have emerged.
We study ultrafast carrier relaxation in Si by means of time-resolved two-photon photoemission
spectroscopy with tunable fs lasers as the pump light. Si samples with (100)-(2x1) and (111)-
(7x7) surfaces were excited with photon energies (hν’s) from near infrared to ultraviolet (1.66 3.5
eV), and temporal population of normally unoccupied surface- and bulk-electronic states were
probed simultaneously by the third harmonics (120 fs, 5.00 eV) of the regenerative amplifier
output. The forth harmonics (150 fs, 6.01 eV) was also used to study the hot-hole dynamics.
First, the intra-valley (X valley) scattering and energy relaxation process have been probed directly.
Photogenerated hot electrons relax down to CBM within 150 fs, forms a quasi-equilibrated
distribution characterized by an effective temperature T* that depends on , and are cooled down
via e-p cooling characterized by a time constant of 240 fs. The highest T* increases with hν, and
about a half of excess energy is maintained in electronic system in the relaxation process. Second,
L-to-X inter-valley scattering process has been probed for hν larger than 3 eV, where direct
transition at L point becomes allowed. The process is characterized by the temperature-dependent
rate constant ( 300 fs at 300 K). Then, the population near CBM is delayed significantly to reach
the maximum at about 0.7 ps after 120-fs pump-pulse excitation. The temperature dependent
feature is governed by available phonons of 43 meV (LA mode along Σ).
The hot-carrier relaxation in bulk states governs the bulk-to-surface electron transfer. For unoccupied
surface state (Ddown) on Si(001)-(2x1), an efficient hot-electron transfer during cooling
determines the initial Ddown population, which is followed by the persistent slow transfer from
cooled electrons at CBM, detected directly by probing a dispersive higher-energy levels of Ddown.
The dynamical transfer to the surface states leads to a significant reduction of CBM electron density
near surface region, and prepares a spatial distribution by which carrier diffusion process is
controlled. The study of hot-hole relaxation near surfaces reveals essentially the same features in
energy relaxation (cooling) and surface recombination processes.
16

Electronic energy transfer
Invited talk Monday 16:00
Spectroscopic probe of polaron and exciton dynamics in organic
semiconductors
MATTHIAS MUNTWILER, QINGXIN YANG, WILLIAM A. TISDALE, and XIAOYANG ZHU
Department of Chemistry, University of Minnesota, Minneapolis, MN 55455, USA
zhu@umn.edu
Charge carrier generation and transport are central to the operation of all organic electronic and
optoelectronic devices, such as organic light-emitting diodes (OLEDs), field effect transistors
(OFETs), and photovoltaic cells (OPVs). A fundamental distinction from their inorganic counter
parts is the localized nature of charge carriers and electronic excitations in organic semiconductors.
Localization results from the narrowness of the electronic band, the flexibility of the
organic molecule, the deformability of the van der Waals bonded lattice, and the low dielectric
constants of organic solids. This is in addition to the prevalence of structural and chemical defects
that form the bulk of charge carrier traps in organic semiconductors. We study polarons
and excitons in organic semiconductors using two spectroscopic approaches. The first approach
relies on in situ IR and NIR spectroscopy to directly monitor molecular vibrations and electronic
transitions associated with charge carriers in gate-doped organic semiconductors. The second approach
uses femtosecond time-resolved two-photon photoemission (TR-2PPE) spectroscopy to
follow the formation and decay of excitons and small polarons in organic semiconductors. These
experiments are beginning to answer the following critical questions:
How do charge carriers separate at organic heterojunctions in an OPV?
How does a charge carrier move in an OFET?
What is the mechanism for the metal-to-insulator transition in a gate doped conducting polymer?
17

Electronic energy transfer
Invited Monday 17:20
Exciton localization, decay and diffusion in carbon nanotubes and
nanotube crystallites
TOBIAS HERTEL
Department of Physics and Astronomy, 6301 Stevenson Center Lane, Vanderbilt University,
TN, USA
Institut für Physikalische Chemie, Am Hubland, Universität Würzburg, D-97074 Würzburg,
Germany
tobias.hertel@phys-chem.uni-wuerzburg.de
Our understanding of energy transfer and -dissipation in carbon nanotubes (CNTs) is essential for
an assessment of their potential use in electronic and optical applications. Here I will concentrate
on discussing our current understanding of a variety of dynamical processes in semiconducting
CNTs and CNT aggregates. We explore the ultrafast dynamics of different excitons in these onedimensional
systems using a linear and non-linear optical probes. Among others will discuss
the role of phonons, defects and metallic tubes for non-radiative decay and photoluminescence
quantum yields in semiconducting CNTs which today can exceed 3%, an improvement of a factor
of 30 from values reported about 5 years ago. This, in combination with recent progress in the
preparation of structurally sorted samples, quite literally provides CNTs with a brighter future
for use in optical and optoelectronic applications.
18

Vibrational energy transfer
Extended talk Monday 18:00
Energy gain process in laser photoemission through excitation of surface
vibrations
RYUICHI ARAFUNE 1 , MAYUKO YAMAMOTO 2 , NORIAKI TAKAGI 2 , YOICHI UEHARA 3 ,
SUKEKATSU USHIODA 4 , and MAKI KAWAI 2,5
1 PRESTO, Japan Science and Technology Agency (JST), Japan
2 Department of Advanced Materials Science, University of Tokyo, Japan
3 Research Institute of Electric Communication, Tohoku University, Japan
4 National Institute for Materials Science, Japan
5 RIKEN, Japan
r-arafune@k.u-tokyo.ac.jp
Recently we have found the energy loss process through excitation of surface vibrations in photoemission
excited by low energy laser light [1,2]. In this presentation we will show that the
energy gain of photoelectron through phonon annihilation exists by analyzing the temperature
(T) dependence (20 K < T < 300 K).
The sample was the oxygen covered Cu(001). The laser photoemission spectra (hν = 4.931 eV)
of this surface contain the inelastic spectral structure arising from the excitation of the surface
longitudinal resonance (19 meV) and two Cu-O frustrated translation modes (53 and 83 meV)[3].
The photoemission intensity at the Fermi level increased with sample temperature. We surmised
that this temperature dependence can be explained by phonon annihilation in the photoemission
process.
As is well known, the intensity of phonon annihilation and creation events are related by the
Boltzmann factor, exp (Evib/kT ). The energy of the longitudinal surface resonance mode is comparable
to the thermal energy above ≈ 200 K. Thus, the phonon annihilation process corresponding
to this mode should not be ignored in the analysis of the low energy photoemission spectra
taken at high temperatures. Indeed, we succeeded in reproducing the temperature dependence
by introducing a spectral component whose shape is the Fermi-Dirac distribution up-shifted by
19 meV and the height is determined by the Boltzmann factor in addition to the energy loss
components. This result confirms that the laser-excited low energy photoelectron interacts with
surface vibrational elementary excitations.
[1] Ryuichi Arafune, Kei Hayashi, Shigenori Ueda, Yoichi Uehara, and Sukekatsu Ushioda, Phys. Rev.
Lett. 95, 207601 (2005)
[2] R. Arafune, K. Hayashi, S. Ueda, Y. Uehara, and S. Ushioda, Surf. Sci. 600, 3536 (2006)
[3] R. Arafune et al., (in preparation).
19

Spin-dependent dynamics and ultrafast magnetization
Extended talk Monday 18:30
Interferometric control of spin-polarized three-photon photoemission from
Cu(001)
AIMO WINKELMANN 1 , WEN-CHIN LIN 1 , FRANCESCO BISIO 2 , HRVOJE PETEK 3,4 , and
JÜRGEN KIRSCHNER 1
1 Max-Planck-Institut für Mikrostrukturphysik, Halle(Saale), Germany
2 CNISM, Sede consorziata di Genova, Dipartimento di Fisica, Genova, Italy
3 University of Pittsburgh, Pittsburgh, USA
4 Donostia International Physics Center DIPC, San Sebastian, Spain
winkelm@mpi-halle.mpg.de
The interaction of circularly polarized light with electronic states that are influenced by spin-orbit
coupling provides a mechanism for selective excitation of spin-polarized electrons in nonmagnetic
and magnetic solids. This type of interaction bears close analogy to the effect of a magnetic
field, and it enables the control of magnetic and other spin-dependent phenomena by optical
means on time scales of the order of the applied laser pulse lengths and electron-hole pair dephasing
times in solids and at solid surfaces.
We demonstrate that we can selectively excite spin-polarized electrons from the spin-orbit split
d-bands of Cu(001) in a three-photon process by using circularly polarized ultrashort optical
pulses. The spin-polarization of the emitted photoelectrons is then interferometrically controlled
by the delay between two pulses in a pump-probe experiment. As a function of pulse delay, the
spin polarization can be changed from ±20% to ∓40% . We differentiate between the regime of
optical interference for overlapping pulses and, for longer delays, the influence of the material
response. The influence of the coherent material response is detected by observing interference
oscillations at twice the optical frequency in the final state population as well as in the spin
polarization.
[1] F. Bisio, M. N´yvlt, J. Franta, H. Petek, and J. Kirschner, Phys. Rev. Lett. 96, 087601 (2006)
[2] A. Winkelmann, F. Bisio, R. Ocaña, W.C.-Lin, M. N´yvlt, H. Petek, and J. Kirschner, Phys. Rev. Lett.
98, 226601 (2007)
[3] A. Winkelmann, W.-C. Lin, F. Bisio, H. Petek, and J. Kirschner, Phys. Rev. Lett. 100, 206601 (2008)
20

19:30 Monday poster
Poster session
M1 Femtosecond electron dynamics in atomic wires: Si(557)-Au
Kerstin Biedermann, Tilman K. Rügheimer, Thomas Fauster, Franz J. Himpsel
M2 The Role of Thermal Activation in Electron Transfer and Solvation at Molecule-Metal Interfaces
Julia Stähler, Uwe Bovensiepen, Michael Meyer, Daniela O. Kusmierek, Martin Wolf
M3 Hot Electron Dynamics at the Bi(111) Surface
Matthias Muntwiler, William A. Tisdale, Xiaoyang Zhu
M4 Photoinduced melting of the Charge Density Wave state in K0.3MoO3
Hanjo Schäfer, Andrej Tomeljak, David Städter, Markus Beyer, K. Biljakovic, Jure Demsar
M5 Determination of the solvated electron binding site on D2O/Cu(111) using Xe adlayers and
femtosecond photoelectron spectroscopy
Michael Meyer, Julia Stähler, Uwe Bovensiepen, Martin Wolf
M6 Charge-transfer dynamics in self-assembled monolayers of azobenzene alkanethiols probed
by the core-hole clock
Roland Schmidt, Robert Carley, Wolfgang Freyer, Cornelius Gahl, Martin Weinelt
M7 Good Vibrations - ultrafast excitation, decay, echoes and hotbands from CO adsorbed on a
metal surface
Heike Arnolds, David A. King, Ian M. Lane
M8 Coherent control of coupled modes in a polar semiconductor using off-resonant pulse train
Jaedong Lee, Muneaki Hase
M9 Momentum-dependence of coherently generated currents at metal surfaces
Jens Güdde, Marcus Rohleder, Ulrich Höfer
M10 Ultra-fast Time Resolved Electron Diffraction at Surfaces
Simone Möllenbeck, B. Krenzer, A. Hanisch, T. Pelka, P. Schneider, M. Horn-von Hoegen
M11 DIET or DIMET? Femtosecond-laser Photodesorption of NO from Supported Ag Nanoparticles
Ki Hyun Kim, Kazuo Watanabe, Dietrich Menzel, Hans-Joachim Freund
M12 Spin-dependent hot electron lifetime - the role of exchange scattering
Andreas Goris, Ilja Panzer, Fabian Giesen, Anke B. Schmidt, Martin Pickel, Markus Donath,
Martin Weinelt
M13 Ultrafast magnetization dynamics in Gd studied by timeresolved XMCD
Marko Wietstruk, Torsten Kachel, Niko Pontius, Christian Stamm, Hermann A. Dürr, Wolfgang
Eberhardt, Alexey Melnikov, Uwe Bovensiepen, Cornelius Gahl, Martin Weinelt
M14 A new apparatus for combined energy- and angle-resolved two-photon photoemission
Christian Eickhoff, Jens Kopprasch, Cornelius Gahl, Robert Carley, Martin Weinelt
M15 Interferometric electron emission measurements at the surface of graphite in the short pulse,
strong field regime
Emma Catton, Andrey Kaplan, Miklos Lenner, Christophe Huchon, Joseph S. Robinson,
Christopher Arrell, John W. G. Tisch, Jonathan P. Marangos, Richard E. Palmer
M16 An angle-resolved time-of-flight spectrometer for the two-dimensional detection of low
energy photoelectrons
Laurenz Rettig, Patrick S. Kirchmann, Uwe Bovensiepen, Martin Wolf
M17 Subwavelength spatio-temporal control of ultrafast nano-optical fields
Martin Aeschlimann, Michael Bauer, D. Bayer, T. Brixner, S. Cunovic, F. Dimler, A. Fischer,
W. Pfeiffer, M. Rohmer, Ch. Schneider, F. Steeb, Christian Strüber, D. V. Voronine
21

Electronic energy transfer M1
Poster Monday 19:30
Femtosecond electron dynamics in atomic wires: Si(557)-Au
KERSTIN BIEDERMANN 1 , TILMAN K. RÜGHEIMER 1 , THOMAS FAUSTER 1 , and FRANZ J.
HIMPSEL 2
1 Lehrstuhl für Festkörperphysik, Universität Erlangen, Germany
2 Department of Physics, University of Wisconsin-Madison, USA
Kerstin.Biedermann@physik.uni-erlangen.de
Atomic wires of noble metals such as gold on silicon surfaces serve as a model system for the investigation
of one-dimensional electron systems. Recent experiments on Si(557)-Au have proven
the existence of a spin-split surface state band below EF [1] and have provided first information
on the unoccupied part of the electronic band structure [2,3]. The dynamics of electrons has not
been investigated so far.
We have carried out time-resolved two-
photon photoemission experiments using
femtosecond laser pulses. Infrared (IR) and
frequency-tripled ultraviolet (UV) radiation
was generated by a Ti:sapphire oscillator.
The figure shows an intensity map as a function
of time delay and kinetic energy. The
high intensity at 0.9 eV kinetic energy and
time delay zero corresponds to an imagepotential
resonance [2,3] and has a lifetime
of less than 10 fs. At lower kinetic energies
the intensity spreads towards positive
as well as nega-
Kinetic energy (eV)
1.0
0.8
0.6
0.4
0.2
Si(557)-Au
IR + UV p-polarized
in mirror plane
-400 -200 0 200 400 600
UV before IR Time delay (fs) IR before UV
tive time delays indicating contributions of several transitions. Around 0.2 eV kinetic energy an
intensity pile-up at positive delays (IR before UV) indicates an indirect filling process of a longlived
state in the bulk band gap of the Si(557) substrate. We present a detailed analysis of the data
which reveals several lifetimes on the femtosecond and the picosecond scale. The interpretation
involves electron scattering between several surface states in the gap.
[1] I. Barke, F. Zheng, T. K. Rügheimer, and F. J. Himpsel, Phys. Rev. Lett. 97, 226405 (2006)
[2] J. A. Lipton-Duffin, J. M. MacLeod, and A. B. McLean, Phys. Rev. B 73, 245418 (2006)
[3] T. K. Rügheimer, Th. Fauster, and F. J. Himpsel, Phys. Rev. B 75, 121401 (2007)
22

M2 Electronic energy transfer
Talk Monday 19:30
The Role of Thermal Activation in Electron Transfer and Solvation at
Molecule-Metal Interfaces
JULIA STÄHLER, UWE BOVENSIEPEN, MICHAEL MEYER, DANIELA O. KUSMIEREK, and
MARTIN WOLF
Freie Universität Berlin, Fachbereich Physik, Arnimallee 14, 14195 Berlin, Germany
j.staehler1@physics.ox.ac.uk
Electron transfer (ET) processes across interfaces are essential in many fields of physics, chemistry,
and biology. Besides their fundamental importance they are also technologically highly
relevant for the development of nanoscale electronic devices or dye-sensitized solar cells. The
solvated electron, which is localized and stabilized in a polar environment such as water or ammonia,
is a model system for the investigation of charge transfer processes at molecule-metal
interfaces. This is due to the transient level of confinement of the solvated electron’s wavefunction,
resulting in a varying degree of overlap with metal states and therefore the transfer rate.
Using femtosecond time-resolved two-photon photoelectron (2PPE) spectroscopy, all involved
fundamental processes are resolved: Electron transfer from the metal substrate into the adsorbate
layer, stabilization of the excess charge, and the competing subsequent back transfer to the metal.
ET is often described in terms of Marcus Theory, considering the nuclear rearrangement of the
solvent along a reaction coordinate q. The transfer process itself, however, occurs via tunnelling
through an interfacial potential barrier, which may be modified by thermally induced fluctuations
of the solvent molecules. We present time- and temperature-dependent studies of the
electron transfer and solvation dynamics at various NH3- and D2O-metal interfaces to highlight
the role of thermally activated tunnelling in heterogeneous electron transfer. It will be shown
that thermal fluctuations of the solvent molecules play (i) a negligible role in the case of strong
electronic coupling between a solvated charge and the metal states and (ii) strongly influence the
ET dynamics if the excess charge is increasingly decoupled from the substrate. The electronic
coupling between excess electron and substrate is strong for amorphous D2O layers on Cu(111)
and Ru(001), leading to temperature-independent ET within the first 500 fs after photoexcitation.
At the NH3/Cu(111) interface, in contrast, the solvated electrons exhibit - depending on layer
thickness - considerably longer lifetimes up to 100 ps, allowing for the observation of thermally
activated tunnelling in the weak coupling limit. Furthermore, due to the transient degree of wave
function overlap of the solvated electrons with metal states, the transition from the strong to the
weak coupling regime is observed in the time domain.
[1] Current affiliation: University of Oxford, Department of Physics, Clarendon Laboratory,
Parks Road, Oxford OX1 3PU, UK
23

Electronic energy transfer M3
Poster Monday 19:30
Hot Electron Dynamics at the Bi(111) Surface
MATTHIAS MUNTWILER, WILLIAM A. TISDALE, and XIAOYANG ZHU
University of Minnesota, Minneapolis, USA
muntw001@umn.edu
The electronic valence structure of semimetal bismuth is governed by a Peierls distortion of the
crystal lattice, which drastically lowers the density of states at the Fermi level [1]. Correspondingly,
the electronic structure is often characterized as a semiconductor with a 0 eV band gap.
These unique properties are also represented indirectly in time-resolved two-photon photoelectron
spectroscopy (TR-2PPE) of the Bi(111)rh surface.
The 2PPE spectrum exhibits two notable features. First, an extended series of image-potential
states (IPS) is observed. While the lowest three states are resolved in the energy domain, higher
lying states up to n = 6 can be inferred from quantum beats in the time domain (similar to the
observations on Cu(001) [2]). The existence of IPS reveals a gap in the projected band structure.
The second feature is a transient hot electron population of the bulk conduction band. It decays
via intraband and interband scattering processes as the average energy and the intensity of
the population decrease over a time scale of a few hundred femtoseconds. Phonon involvement
in interband scattering connects our observation to time-resolved X-ray diffraction experiments
where transient phonon softening and transient lifting of the Peierls distortion after photoexcitation
have been reported [3].
log(intensity)
cond. band
317 fs
-1000 -500 0
t (fs)
E - E F (eV)
1.0
0.5
log(intensity)
0.0
0.5
1.0
-1000 -500 0
UV probe t (fs) IR probe
[1] P. Hofmann, Prog. Surf. Sci. 81, 191 (2006), and references therein
[2] U. Höfer et al., Science 277, 1480 (1997)
[3] D. M. Fritz et al., Science 315, 633 (2007)
24
E B (eV)
0
image states
n = 4, 5, 6
quantum beats
n = 3
250 fs
n = 2
82 fs
n = 1
12 fs
500
t (fs)
1000
intensity

M4 Electronic energy transfer
Poster Monday 19:30
Photoinduced melting of the Charge Density Wave state in K0.3MoO3
HANJO SCHÄFER 1 , ANDREJ TOMELJAK 1,2 , DAVID STÄDTER 1 , MARKUS BEYER 1 , KATICA
BILJAKOVIC 3 , and JURE DEMSAR 1,2
1 Physics Dept., Konstanz University, Konstanz, Germany
2 J. Stefan Institute, Ljubljana, Slovenia
3 Institute of Physics, Zagreb, Croatia
hanjo.schaefer@uni-konstanz.de
In superconductors, it has been known for decades that the intense laser pulse can non-thermally
destroy the superconducting ground state [1]. The energy required to destroy superconductivity
should, in the case that all absorbed energy is kept in the electronic subsystem during the process
of suppression of superconductivity, be equal to the condensation energy (energy difference
between the free energy of the SC and normal states). In recent experiments on MgB2 [2] and
La2−xSrxCuO4 [3] it has been shown, however, that the absorbed optical energy required to suppress
superconductivity is substantially higher than the condensation energy. This was explained
by the fact that in the process of destruction of the SC state a large portion of the absorbed energy
density is stored in the bosonic subsystem which equilibrates with quasiparticles on the ps
timescale [2,3].
Here we have studied the photoexcited carrier and collective mode dynamics in the prototype
quasi-1D charge density wave (CDW) system K0.3MoO3 aiming to determine the absorbed energy
density needed to completely suppress the CDW order. We find that the absorbed energy
density required to melt the CDW state at 4K is Esat ≈ 75 meV/unit cell volume. This energy
density is about an order of magnitude lower than the energy required to heat the excited volume
to above the phase transition implying that melting of the long range CDW order is achieved
non-thermally similarly as in superconductors. On the other hand we can compare Esat with
the analogue of the superconducting condensation energy, Ec, which can be estimated as Ec =
N(Ef)∆ 2 /2, where N(Ef) is the normal state density of states at Fermi level and ∆ is the value of
the gap. Using published values of ∆ and N(Ef) we obtain Ec = 5-10 meV, which is substantially
lower than the experimentally measured energy density needed to destroy the CDW state with
optical excitation. This suggests that in the ultrafast process of initial thermalization of highly
excited e-h pairs, part of the energy is stored in the lattice subsystem in the same manner as in
superconductors.
[1] L. R. Testardi, Phys. Rev. B 4, 2189 (1971).
[2] J. Demsar et al., Phys. Rev. Lett. 91, 267002 (2003); J. Demsar et al., Int. J. Mod. Phys. B 17,
3675 (2003).
[3] P. Kusar et al., submitted
25

Electronic energy transfer M5
Poster Monday 19:30
Determination of the solvated electron binding site on D2O/Cu(111) using
Xe adlayers and femtosecond photoelectron spectroscopy
MICHAEL MEYER, JULIA STÄHLER, UWE BOVENSIEPEN, and MARTIN WOLF
Department of Physics, Freie Universität Berlin, Germany
meyerm@physik.fu-berlin.de
The solvation dynamics of excess electrons is well studied in a variety of different polar molecular
layers adsorbed on various substrates [1]. Beside interesting localization and stabilization
dynamics these electrons have a high capability to enhance the chemical reactivity with coadsorbed
molecules such as chlorofluorocarbons [2]. The efficiencies of these reactions can even
be more enhanced when the lifetime of the solvated electrons is increased or the electron density
resides at the molecule-vacuum interface. Thus, information on the electrons binding site is
of interest. The present study investigates by means of 2PPE spectroscopy the binding site of
solvated electrons in amorphous D2O clusters and D2O wetting layers adsorbed on Cu(111). The
question we focus on is whether the localized excess electron resides at the surface or in the bulk
of the molecular adlayer. On the basis of different interactions between bulk- or surface- bound
electrons and rare gas atoms, titration experiments using Xe adlayers adsorption revealed the
location of the electron solvation sites. In the case of clusters, the binding energy of the solvated
electrons was decreased by 400 meV upon Xe exposure. This strong effect can only be explained
by the direct interaction of the rare gas atoms with solvated electrons residing at the ice-vacuum
interface. No shift of the solvated electron distribution in the 2PPE spectra after xenon adsorption
was found in wetting layers revealing their bulk bound character. The ultrafast transfer and
stabilization dynamics of the electrons is sensitive to their interaction with the substrate, i.e.
their position on the cluster surface. To specify the binding site of the surface bound electrons in
clusters, their ultrafast transfer dynamics was used as an indicator. Indeed, applying an empirical
model calculation to reproduce the back transfer dynamics and the energetic stabilization of the
solvated electrons [3], allowed concluding on the character of the ice-vacuum interface binding
site of the clusters. We found that the solvated electrons reside at the perimeter of the clusters.
Therefore, we associate the transition between surface- and bulk-solvation to the coalescence of
the clusters to a closed ice film, while the distance of the binding sites to the metal-ice interface
is likely to be maintained.
[1] J. Zhao et al., Chem. Rev. 106, 4402 (2006); P. Szymanski, et al., Prog. Surf. Sci. 78, 1 (2005);
U. Bovensiepen, Prog. Surf. Sci. 78, 87 (2005)
[2] Q. B. Lu et al., Phys. Rev. B 63, 153403 (2001); S. Ryu et al., J. Am. Chem. Soc. 128, 3500
(2006); M. Bertin et al., Faraday Discussion, submitted (2008)
[3] J. Stähler et al., J. Phys. Chem. B 110, 9637 (2006)
26

M6 Electronic energy transfer
poster Monday 19:30
Charge-transfer dynamics in self-assembled monolayers of azobenzene
alkanethiols probed by the core-hole clock
ROLAND SCHMIDT 1 , ROBERT CARLEY 1 , WOLFGANG FREYER 1 , CORNELIUS GAHL 1 , and
MARTIN WEINELT 1,2
1 Max-Born-Institut, Max-Born-Straße 2 A, 12489 Berlin, Germay
2 Freie Universität Berlin, Fachbereich Physik, Arnimallee 14, 14195 Berlin, Germany
carley@mbi-berlin.de
Molecular motion induced by optical excitation provides a new prospect for the functionalization
of surfaces on the nanoscale. In this context azobenzene-based photo-switches are widely
explored prototype systems. The azobenzene molecule has two isomers; optical excitation
switches reversibly between the thermally stable trans-form and the metastable cis-form. The
(sub)picosecond time constant of this isomerization reaction in solution yields a quantum efficiency
close to unity [1,2] and switching is possible even with a photodiode. However, when the
bare azobenzene molecule is adsorbed at a metal surface the molecule becomes inoperable as a
photo-switch most likely due to ultrafast charge transfer into the substrate which quenches the
optical excitation.
A promising candidate to overcome this problem are self-assembled monolayers (SAMs). Alkanethiols
are known to form well-ordered SAMs on gold surfaces which are easily prepared by
immersion. Due to the specific chemical bond between the thiol head-group and the gold surface
as well as lateral interactions, self-assembled layers of alkanethiols are well-ordered. In this work
the alkane chains are used to decouple the azobenzene switch from the thiol head-group which
in turn acts as the linker to the gold surface. We synthesized molecules with alkane chain-lengths
of n = 3, 6, and 10 and the chromophore attached via a single oxygen bond in the para position
of the first phenyl ring.
While the azobenzene entity is sufficiently decoupled from the metal substrate by the alkane
chain, lateral interactions between neighboring molecules within the SAM strongly influence
properties and functionality of the optical switch. The optical absorption spectrum significantly
differs from that in solution and no photo-isomerization is observed. This is attributed to lateral
charge transfer between the chromophores in the densely packed layer. We employed Resonant-
Raman Auger to investigate this charge transfer dynamics among the molecules. The spectra
show sizeable non-resonant contributions which are unaffected by the alkane chain-length. demonstrating
charge delocalization on the time scale of the core hole lifetime of about 6 fs. Introducing
defects into the SAM by X-ray beam damage re-activates the photochromic molecular
switch.
[1] T. Nägele, R. Hoche, W. Zinth, and J. Wachtveitl, Chem. Phys. Lett. 272, 489 (1997)
[2] T. Fujino, S. Y. Arzhantsev, and T. Tahara, J. Phys. Chem. A 105, 8123 (2001)
27

Vibrational energy transfer M7
Poster Monday 19:30
Good Vibrations - ultrafast excitation, decay, echoes and hotbands from
CO adsorbed on a metal surface
HEIKE ARNOLDS 1 , DAVID A. KING 2 , and IAN M. LANE 2
1 Surface Science Research Centre, University of Liverpool, UK
2 Department of Chemistry, University of Cambridge, UK
Heike.Arnolds@liv.ac.uk
We present a set of experiments that provide a complete mapping of coherent and incoherent
vibrational relaxation times for a molecule on a metal surface, CO/Ir(111), including midinfrared
photon echoes from a metallic surface. For the C–O stretch in a strongly dipole-coupled CO layer
at 0.56 ML coverage we obtain a total linewidth of 5.6 cm −1 , composed of a homogeneous width
of 2.7 cm −1 and an inhomogeneous contribution of 3.0 cm −1 [1].
We contrast this with IR pump-probe measurements at low CO coverage to observe vibrational
ladder climbing through the detection of a transient υ = 1 ← 2 hot band [2].
CO SFG signal / a.u.
100
80
60
40
20
0
1950
2000
2050
frequency / cm -1
t = 0 ps
no pump
0
2100
IR pump-probe spectrum for delay of t = 0 ps and scaled no pump spectrum. The shoulder
at lower frequency to the fundamental is a transiently observed hotband. Coverage of CO on
Ir(111) is 0.15 ML.
[1] Ian M. Lane, David A. King, Heike Arnolds, J. Chem. Phys. 126, 024707 (2007)
[2] Heike Arnolds, Ian M. Lane, to be published.
28
200
150
100
50
CO no pump SFG intensity/ a.u.

M8 Coherent phenomena
Poster Monday 19:30
Coherent control of coupled modes in a polar semiconductor using
off-resonant pulse train
JAEDONG LEE 1 and MUNEAKI HASE 2,3
1 School of Materials Science, Japan Advanced Institute of Science and Technology, Japan
2 Institute of Applied Physics, University of Tsukuba, Japan
3 PRESTO, Japan Science and Technology Agency, Japan
jdlee@jaist.ac.jp
Investigating the nonequilibrium ultrafast dynamics of the coherent phonon-plasmon coupled
modes in a polar semiconductor, we find that their coherent oscillations can be efficiently controlled
by using the off-resonant pulse train. The dynamics of the coherent modes are driven by
the virtual electron-hole pairs, which would avoid the dephasing sources such as the accumulation
of photoexcited charges and the spontaneous emission. This implies that the carrier mobility
[1] can be dramatically enhanced by synchronizing the off-resonant pulse train with the coherent
oscillation of the carrier-relevant (plasmon-like) coupled mode.
[1] M. Hase, unpublished (2008).
29

Coherent Phenomena M9
Poster Monday 19:30
Momentum-dependence of coherently generated currents at metal surfaces
JENS GÜDDE, MARCUS ROHLEDER, and ULRICH HÖFER
Fachbereich Physik und Zentrum für Materialwissenschaften, Philipps-Universität, D-35032
Marburg, Germany
Jens.Guedde@physik.uni-marburg.de
Recently we have shown that elastic electron scattering in excited states at surfaces can be directly
observed in k-space by measuring the momentum-resolved incoherent population dynamics
using time- and angle-resolved photoelectron spectroscopy in combination with a coherent optical
excitation scheme [1]. Phase-locked ultrashort laser-pulses at frequencies ωa and 2ωa were
used to generate a coherently controlled current in image-potential states of a Cu(100) surface,
which is detected as asymmetry A = (I + − I − )/(I + + I − ) of the photoemission intensities I +
and I − for opposite parallel momenta of the photoemitted electrons +k� and −k�, respectively.
The decay of the asymmetry A gives direct information about the redistribution of the electrons
within the excited band due to elastic scattering processes. The asymmetry A can be controlled
by the relative phase between the excitation pulses as shown Fig. 1. For Cu(100) the initial state
is in fact a continuum of states given by the projected s/p-band and the image-potential band is
uniformly populated for a given direction of k�. As depicted in Fig. 1 this results in the observation
of a current over the whole excited image-potential band, which increases monotonously
with parallel momentum. In this contribution we will compare these results on Cu(100) with
recent results on Cu(111) where the Shockley surface state forms a two-dimensional band with
an effective mass which is more than a factor of two smaller as compared to the image-potential
bands. This leads to a resonant enhancement of the population and therewith the current for a
specific parallel momentum that can be selected by the photon energy.
Momentum k II ( –1 )
0.20
0.15
0.10
0.05
0.00
–360° –180° 0 180° 360° 540°
Phase between ωa and 2ωb 0.05
0.00
–0.05
(I + –I – )/(I + +I – )
Fig. 1: Asymmetry of the photoemission intensity
for opposite parallel momenta ±k� on
Cu(100) as a function of k� and as a function of
the relative phase between the excitation pulses
at frequencies ωa and 2ωa.
[1] J. Güdde, M. Rohleder, T. Meier, S. W. Koch, and U. Höfer, Science 318, 1287 (2007)
30

M10 Wave-packet dynamics
Poster Monday 19:30
Ultra-fast Time Resolved Electron Diffraction at Surfaces
SIMONE MÖLLENBECK, B. KRENZER, A. HANISCH, T. PELKA, P. SCHNEIDER, and M.
HORN-VON HOEGEN
Department of Physics, Universität Duisburg-Essen, D-47057 Duisburg, Germany
simone.moellenbeck@uni-due.de
Ultra-fast time resolved reflection high energy electron diffraction (TR-RHEED) is a powerful
tool to study the thermal conductance of thin Bismuth-films on Silicon [1-3]. The surface sensitivity
in the RHEED-geometry was used to analyze the structural dynamics on a ps-timescale. In a
pump-probe setup the transient surface temperature evolution upon excitation with fs-laser pulses
is observed. The spot intensities taken at different time delays between pumping laser pulses and
probing electron pulses are converted into transient surface temperature using the Debye-Waller
Effect.
Here we extended the possibilities of TR-RHEED to study monolayer adsorbate systems and
nano structured islands. Both are present for deposition of Pb on Si(111), where Pb forms the
( √ 3 × √ 3) Pb/Si(111) adsorbate system with coexisting Pb-islands on Si(111). This allows us
to observe the transient surface temperature of a Pb monolayer and simultaneously the bulk
properties of Pb islands. It is a unique possibility of time resolved electron diffraction in RHEEDgeometry
to observe not only surface dynamics but also at the same time bulk dynamics.
Both the ( √ 3 × √ 3) Pb monolayer and the Pb islands show up with different spots in the diffraction
pattern. Thus we have the possibility to compare the transient temperature evolution of these
two different systems simultaneously in only one experiment. We attribute the decay constant
of 200 ps to the lead islands. This result is in good agreement with the theory for heat transport
across an abrupt hetero interface. The decay constant of the remaining set of spots is as large as
2000 ps. From this astonishing result we have to conclude, that the thermal coupling of a lead
monolayer to the Silicon substrate is extremely poor - the heat is trapped in the Pb monolayer.
A further possibility to use TR-RHEED is the observation of the dynamics of phase transitions
at surfaces. We studied the famous order-disorder transition from Si(001)c(4×2) to (2×1) [4].
First preliminary results show a reversible drop of the intensity by 7% upon excitation by 800 nm
fs-laser pulses. The intensity of the c(4×2) spots recovers slowly with a time constant of several
hundred ps. This result agrees surprisingly well with literature values on the excitation of the
electron system [5].
[1] B. Krenzer et al., New J. Phys. 8, 190 (2006).
[2] A. Janzen et al., Rev. Sci. Instrum. 78, 013906 (2007).
[3] A. Hanisch et al., Phys. Rev. B 77, 125410 (2008).
[4] T. Tabata, T. Aruga, and Y. Murata, Surf. Sci. 179, L63 (1987).
[5] M. Weinelt et al., Phys. Rev. Lett. 92, 126801 (2004).
31

Laser-induced photochemical reactions M11
Poster Monday 19:30
DIET or DIMET? Femtosecond-laser Photodesorption of NO from
Supported Ag Nanoparticles
KI HYUN KIM 1 , KAZUO WATANABE 1 , DIETRICH MENZEL 1,2 , and HANS-JOACHIM
FREUND 1
1 Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
2 Physik-Department E20, Technische Universität München, 85748 Garching, Germany
watanabe@fhi-berlin.mpg.de
Photochemistry of molecules adsorbed on metal nanoparticles can significantly differ from those
on planar bulk metal surfaces [1]. It may show strong size dependences in photodesorption cross
sections and kinetic energies of photodesorbates [2]. In this presentation, we report on drastic
changes in reactivity and dynamics of photodesorption of NO induced by femtosecond laser
pulses from alumina supported Ag nanoparticles (AgNPs), in comparison with Ag(111).
A monolayer of NO dimers were formed on either AgNPs (mean diameter of 8 nm) deposited
on Al2O3/NiAl(110) or Ag(111) by exposure to NO at 75 K in an ultrahigh vacuum chamber.
Photodesorption of NO from these layers were induced by 3.1-eV photons (80 fs, 0.01 - 2
mJ/cm 2 ) and detected by a quadrupole mass spectrometer. The photodesorption cross sections
(PCS) and the translational temperature (Tt) of desorbed NO were obtained from the decay of
the photoinduced desorption (PID) signal, and by fitting time-of-flight spectra to a sum of shifted
Maxwell-Boltzmann distributions, respectively.
The PCS of NO from Ag(111) was about 4×10 −18 cm 2 and similar to that measured with nanosecond
laser pulses. In contrast, the PCS of NO from the AgNPs was extremely high, 4×10 −14
cm 2 . In both cases, the PCS was independent of the laser fluences, and the initial PID yield was
proportional to the laser fluence. These results are consistent with the DIET (desorption induced
by electronic transitions) mechanism.
However, the Tt of NO desorbed from the AgNPs increased linearly with laser fluence from 600
K to 1700 K at 2 mJ/cm 2 while that from Ag(111) was almost constant at ∼600 K. The AgNP
result is more consistent with the DIMET (desorption induced by multiple electronic transitions)
picture.
The anomalously high PCS values and the Tt increasing with laser fluence must be connected to
peculiarities of electron dynamics in the AgNPs. Possible models will be presented and discussed.
References
[1] K. Watanabe, D. Menzel, N. Nilius, and H.-J. Freund, Chem. Rev. 106, 4301 (2006).
[2] D. Mulugeta, K. H. Kim, K. Watanabe, D. Menzel, and H.-J. Freund, submitted.
32

M12 Spin-dependent dynamics and ultrafast magnetization
Poster Monday 19:30
Spin-dependent hot electron lifetime - the role of exchange scattering
ANDREAS GORIS 1 , ILJA PANZER 1 , FABIAN GIESEN 1 , ANKE B. SCHMIDT 3 , MARTIN
PICKEL 3 , MARKUS DONATH 3 , and MARTIN WEINELT 1,2
1 Max-Born-Institut, Berlin, Germany
2 Freie Universität, Berlin, Germany
3 Physikalisches Institut, Westfälische Wilhelms-Universität, Münster, Germany
goris@mbi-berlin.de
The lifetime of hot electrons in 3d ferromagnetic thin films is still controversely discussed. Experimentally
found values of the lifetime ratio (τmaj/τmin) are by a factor of 4-5 smaller than
predicted by values of modern ab-initio calculations [1,2].
We have measured the spin-dependent hot-electron lifetime for a 20 ML Co film on Cu(001) at
varying excitation density with spin-resolved two-photon photoemission for electron energies
between 250 and 750 meV above EF . A 826 nm laser-pulse was used as an excitation source
while a time-delayed 275 nm pulse lifted the electrons above the vacuum energy. We identify
three contributions to the time resolved spectra: the off-resonant excitation of the image-potential
state, the hot electron decay, and the signature of a spin flip exchange-scattering process with an
occupied surface-resonance state. In this process a hole in the minority surface is filled while a
majority valence electron is in turn lifted above the Fermi level. The minority surface resonance
was recently identified in spin-resolved one- and two-photon-photoemisson studies and theoretically
supported by self-consistent fully relativistic density functional theory calculations [3]. Our
results show that measurements of the spin-dependent hot electron lifetimes with photoemission
techniques are strongly influenced by the surface electronic structure. For a comparison with
theoretical results the latter has to be taken into account.
[1] M. Aeschlimann et. al., Phys. Rev. Lett. 79, 5158 (1997)
[2] V. P. Zhukov et. al., Phys. Rev. Lett. 93, 096401 (2004)
[3] A. B. Schmidt et. al., J. Phys. D., in press (2008)
33

Spin-dependent dynamics and ultrafast magnetization M13
Poster Monday 19:30
Ultrafast magnetization dynamics in Gd studied by timeresolved XMCD
MARKO WIETSTRUK 1 , TORSTEN KACHEL 1 , NIKO PONTIUS 1 , CHRISTIAN STAMM 1 ,
HERMANN A. DÜRR 1 , WOLFGANG EBERHARDT 1 , ALEXEY MELNIKOV 2 , UWE
BOVENSIEPEN 2 , CORNELIUS GAHL 3 , and MARTIN WEINELT 2,3
1 BESSY GmbH, Berlin, Germany
2 FB Physik, Freie Universität Berlin, Germany
3 Max-Born-Institut Berlin, Germany
marko.wietstruk@bessy.de
In order to improve heat assisted magnetic recording techniques, the understanding of ultrafast
magnetization processes especially the flow of energy and angular momentum is essential. The
demagnetization of a thin gadolinium film has been investigated in the 100 fs to 100 ps regime
after excitation of the 5d6s valence electrons by a 100 fs IR laser pulse. The measurements were
done at the fs-slicing facility at BESSY in low-α and slicing mode. Using circularly polarized
synchrotron radiation we measured X-ray magnetic circular dichroism (XMCD) at the Gd M4,5
absorption edges, a method which provides access to the 4f spin and orbital momentum.
The measurements, presented in the figure, show that the demagnetization process is divided into
two steps. First, a ’fast’ demagnetization occurs with a reduction of the sample magnetization by
∼ 25% within the first picoseconds after excitation. This is followed by a further decrease of the
magnetic signal with a time constant of 40 ps. While the latter time scale corroborates earlier
observations [1] and is assigned to spin-lattice relaxation, the first component suggests ultrafast
demagnetization via the exchange interaction between the 5d6s valence and the 4f core electrons.
[1] A. Vaterlaus et al., Phys. Rev. Lett. 67, 3314 (1991)
34

M14 Advances in ultrafast surface spectroscopies
Poster Monday 19:30
A new apparatus for combined energy- and angle-resolved two-photon
photoemission
CHRISTIAN EICKHOFF, JENS KOPPRASCH, CORNELIUS GAHL, ROBERT CARLEY, and
MARTIN WEINELT
Max-Born-Institut, Max-Born-Str. 2a, 12489 Berlin, Germany
eickhoff@mbi-berlin.de
A new apparatus is presented which allows for detection of the energy and the angle of photoemitted
electrons at the same time in a two-photon photoemission experiment (2PPE). Spectra
are collected using a hemispherical energy analyzer(Phoibos 100, SPECS) equipped with a lens
system for isogonal deflection of the electrons and a 2D-CCD detector. Since we are able to
introduce a time delay between the pump and probe-pulse, time-resolved measurements are also
possible. A newly built laser system based on a Ti:Sa regenerative amplifier generates 800 nm
pulses of 50 fs duration. Subsequent parametric amplification and second harmonic generation
provides 70 fs ultraviolet pulses with photon energies between 1.8 and 5.5 eV.
Since the Cu(111) surface is a well known system, we studied the surface states to characterize
the analyzer. In addition further experiments show a k||-and temperature-dependent lifetime of
the electrons in the first and the second image-potential states.
We have also investigated the dangling-bond and image-potential states on the Si(100) 2 × 1 surface.
The available photon energies allow us to populate unoccupied states up to the Si(100) vacuum
level. Besides the occupied dangling-bond state Dup, we resolve the first two image-potential
states n = 1 and n = 2. In previous experiments, significant variation of both the 2PPE peak
positions and intensities were found when tuning the photon energy of the pump pulse across the
Dup to n = 1 and Dup to n = 2 transitions. Before resonance we observe the Dup initial state
with the kinetic energy increasing as the pump-pulse photon-energy. Above resonance the Dup
intensity is significantly reduced and shifted to the respective image-potential-state resonances
at constant kinetic energy. These intensity variations point towards an interference between transitions
to the discrete image-potential-state resonances and to the continuum of unoccupied bulk
states.
35

Advances in ultrafast surface spectroscopies M15
Poster Monday 19:30
Interferometric electron emission measurements at the surface of graphite
in the short pulse, strong field regime
EMMA CATTON 1 , ANDREY KAPLAN 1 , MIKLOS LENNER 1 , CHRISTOPHE HUCHON 1 , JOSEPH
S. ROBINSON 2 , CHRISTOPHER ARRELL 2 , JOHN W. G. TISCH 2 , JONATHAN P. MARANGOS 2 ,
and RICHARD E. PALMER 1
1 Nanoscale Physics Research Laboratory, University of Birmingham, England
2 Blackett Laboratory, Imperial College London, England
emma@nprl.ph.bham.ac.uk
Recently it has been shown that the combination of extremely short IR and XUV pulses, as
traditionally employed in gas phase experiments, may be applied to the surface and successfully
used to measure electronic processes in real time 1 . Such advances have helped to trigger a fast
growing interest in what is a challenging yet exciting field.
In this work we have used IR pulses of duration ∼10fs to investigate electron behaviour at the
surface of graphite in the presence of a strong laser field (∼ 10 11 W/cm 2 ). Time of Flight (ToF)
spectroscopy has been used to measure photoelectrons emitted from the surface. The ToF spectra
reveal three energy bands centred at kinetic energies of 0.4eV, 3-6eV and 20-40eV respectively.
In the last case, the emission process is characterised by a high order of nonlinearity (n∼17) yet
the observed electron yield is far greater than would be probable via multiphoton excitation. The
lifetimes of each process have been estimated via interferometric autocorrelation measurements
and there is evidence of surface plasmon involvement. Fast electrons observed are therefore attributed
to plasmon enhancement of the laser field at the surface and subsequent tunnel ionisation.
XUV pulse trains have also been generated in the lab using High Harmonic Generation (HHG)
and the resulting photoelectron spectra can be used to study the structure of the valence band
at the surface. Similarities between these spectra and those taken with IR lend further weight
to the proposed plasmon assisted tunnelling mechanism. Preliminary XUV - IR pump probe
measurements will also be discussed.
[1] A. L. Cavalieri et al., Nature 449, 1039 (2007)
36

M16 Advances in ultrafast surface spectroscopies
Poster Monday 19:30
An angle-resolved time-of-flight spectrometer for the two-dimensional
detection of low energy photoelectrons
LAURENZ RETTIG, PATRICK S. KIRCHMANN, UWE BOVENSIEPEN, and MARTIN WOLF
Fachbereich Physik, Freie Universität Berlin, Germany
laurenz.rettig@physik.fu-berlin.de
Studying the electron scattering dynamics of laterally anisotropic electronic systems such as selfassembled
quasi-1D atomic nano-wires [1], charge-density-wave (CDW) compounds or stepped
surfaces is of great interest to understand the influence of symmetry and dimensionality on the
scattering rates. Such studies would benefit from new detection techniques in photoelectron spectroscopy
which allow to determine both surface in-plane electron momentum components px and
py along with the kinetic energy at the same time.
To satisfy this need we developed and constructed a two-dimensional position-sensitive time-offlight
spectrometer (pTOF) for the angle-resolved analysis of low-energy electrons photoemitted
from metallic surfaces by femtosecond laser pulses [2]. The spectrometer design combines a
field-free drift tube with 22 ◦ acceptance angle and a microchannel plate stack (MCP) with a
delay-line anode [3,4] for position encoding. With this setup, we achieve a high energy and
momentum resolution as well as an excellent signal-to-noise ratio necessary to investigate small
transient changes in time- and angle-resolved direct photoemission (TR-ARPES).
We present the working principles along with the hard- and software implementation of the
pTOF, which includes real-time analysis of multiple electron hits per laser pulse. This multihit
capability is crucial for pulsed laser spectroscopy with repetition rates of upto 100 kHz. To demonstrate
the performance of the spectrometer, direct photoemission measurements on a Cu(111)
single-crystalline surface were performed using UV femtosecond laser pulses of 6.20 eV photon
energy.
[1] S. Yeom et al., Phys. Rev. Lett. 82, 4898 (1999)
[2] P. S. Kirchmann et al., Appl. Phys. A 91, 211 (2008)
[3] O. Jagutzki et al., IEEE Trans. Nucl. Sci. 49, 2477 (2002)
[4] RoentDek Handels GmbH, Germany, http://www.roentdek.com/
37

Advances in ultrafast surface spectroscopies M17
Poster Monday 19:30
Subwavelength spatio-temporal control of ultrafast nano-optical fields
MARTIN AESCHLIMANN 2 , MICHAEL BAUER 4 , DANIELA BAYER 2 , TOBIAS BRIXNER 3 ,
STEFAN CUNOVIC 1 , FRANK DIMLER 3 , ALEXANDER FISCHER 2 , WALTER PFEIFFER 1 ,
MARTIN ROHMER 2 , CHRISTIAN SCHNEIDER 2 , FELIX STEEB 2 , CHRISTIAN STRÜBER 1 , and
DMITRI V. VORONINE 3
1 Fakultät für Physik, University of Bielefeld, Germany
2 Fakultät für Physik, University of Kaiserslautern, Germany
3 Institut für Physikalische Chemie, University of Würzburg, Germany
4 Institut für Experimentelle und Angewandte Physik, University of Kiel, Germany
strueber@physik.uni-bielefeld.de
Using time-resolved two-photon photoemission electron microscopy we demonstrate simultaneous
spatial and temporal control of nanooptical fields. The excitation of a nanostructure with
polarization-shaped laser pulses allows controlling the subwavelength spatio-temporal field distribution
opening a route towards new ultrafast spectroscopy tools on the nanoscale [1]. Based on
the recent demonstration of ultrafast adaptive near field optics using the combination of polarization
pulse shaping and two-photon photoelectron emission microscopy [2] we now investigate
the temporal evolution of the field distribution by cross correlation measurements. These experiments
demonstrate for the first time the mapping of the subwavelength field evolution in the
vicinity of a nanostructure. Different regions of the nanostructure show a clear variation of their
relative intensities within time scales limited only by the spectral bandwidth of the used coherent
light source.
[1] T. Brixner, F. J. García de Abajo, J. Schneider, and W. Pfeiffer, Phys. Rev. Lett. 95, 093901
(2005)
[2] M. Aeschlimann, M. Bauer, D. Bayer, T. Brixner, F. J. García de Abajo, W. Pfeiffer, M.
Rohmer, C. Spindler, and F. Steeb, Nature 446, 301 (2007)
38

Spin-dependent dynamics and ultrafast magnetization
9:00 Ultrafast Magnetization
Joachim Stöhr
Tuesday morning
9:40 Exploring dynamical Magnetism: From microscopic spin-flip mechanisms to Gilbert damping
Martin Aeschlimann
10:20 Coffee break
11:00 Femtosecond electron localization and transfer of angular momentum in ferromagnetic Ni
and Gd
Hermann A. Dürr, N. Pontius, C. Stamm, T. Kachel, M. Wietstruk, W. Eberhardt, C. Gahl,
M. Weinelt, A. Melnikov, M. Sultan, U. Bovensiepen
11:20 Non-equilibrium surface and bulk spin-dynamics at Gd(0001)
Alexey Melnikov, H. Prima-Garcia, M. Wietstruk, M. Sultan, T. Kachel, N. Pontius, C.
Stamm, R. Schmidt, M. Lisowski, T. Gießel, R. Weber, C. Gahl, N. Bulgakova, T. Wehling,
U. Bovensiepen, M. Weinelt, H. Dürr, A. Lichtenstein, M. Katsnelson, W. Eberhardt
11:50 Image-potential states – Observer states for ultrafast magnetization dynamics
Anke B. Schmidt, Martin Pickel, Markus Donath, Martin Weinelt
12:20 Break
12:30 Lunch
13:30 Excursion to Bamberg
39

Spin-dependent dynamics and ultrafast magnetization
Invited talk Tuesday 9:00
Transformation of Magnetic Metals by Extreme Terahertz Fields
JOACHIM STÖHR and HANS C. SIEGMANN
SSRL Stanford, USA
stohr@slac.stanford.edu
Ultra-short high power optical laser pulses have long been used for the creation and study of
materials in extreme conditions. At the largest laser intensities, photoelectric excitation results
in severe heating, melting or even plasma formation. In order to avoid such deleterious interband
excitations, significant efforts have gone into creating lower frequency terahertz (1 THz
= 10 12 Hz) fields with laser-like field amplitudes. Such half-cycle THz pulses act like ultrastrong
unipolar field pulses. This talk will discuss experiments with THz-like ∼ 100 fs pulses of
unprecedented field strengths of up to 20 GV/m, produced by compressing a highly relativistic
electron bunch. Using the magnetic response of a thin film magnetic metal as a diagnostic tool, we
observe two completely new phenomena, the deformation of the characteristic B-field induced
magnetic pattern, and the lack of any discernable temperature rise or damage of the sample.
We discuss our observations as transformational changes in the electronic and magnetic structure
of the metallic sample by the injected ultrashort and ultrastrong electric field. First, the size of
the electric field over atomic dimensions (∼1 V/atom) rivals bonding-type fields and leads to an
ultrafast distortion of the charge within the atomic volume along the field direction. This distortion
leads to a novel magneto-electronic anisotropy which causes a motion of the magnetization
and modifies the magnetic pattern created by the B field. In fact, it is strong enough to switch
the magnetization. Second, the field induced gradient in the atomic potentials along the field direction
disrupts the periodic band structure, and causes the metal to temporarily (over the 100 fs
duration of the field pulse) become an insulator. Any current-induced Joule heating is therefore
avoided and the metal remains cold.
40

Spin-dependent dynamics and ultrafast magnetization
Invited talk Tuesday 9:40
Exploring dynamical Magnetism: From microscopic spin-flip mechanisms
to Gilbert damping
MARTIN AESCHLIMANN
Department of Physics, TU Kaiserslautern, 67663 Kaiserslautern
ma@physik.uni-kl.de
We devote to the very fundamental question of how to excite the spin system with femtosecond
optical pulses. Focus is put on the microscopic processes leading to a spin-flip. By combining
the two complementary experimental concepts of spin-, energy- and time-resolved two photonphotoemission
(2PPE) and time-resolved magneto-optical Kerr effect (TR-MOKE) we have the
experimental potential to directly address the microscopic view of the relevant spin-flip process
responsible for the ultrafast changes in the macroscopic magnetization of a thin Cobalt film.
In particular we find that electron-magnon excitation does not affect the overall magnetization
even though it is an efficient spin-flip channel on the sub-200 fs time scale. Instead we extracted
an Elliot-Yafet (EY) type like process as the origin of demagnetization taking place within 300
fs. In such a process electron-lattice or electron-impurity scattering events are with a certain
probability, depending on the spin-mixing, accompanied by a spin-flip [1,3]. Here the phonon
system acts as an active sink to allow the conservation of the system’s total angular momentum.
We further investigated magnetic Heusler compounds which can be made as half metals possessing
a band gap in the minority spin channel. Heusler compounds therefore serve as a well
suited test material to study the effect of the electronic bandstructure on spin dynamics without
any disturbing effect of unpolarized sp-electrons [2]. Macrospin dynamics is dictated by the
well-known Landau-Lifshitz-Gilbert equation (LLG) describing a precessional motion whose
relaxation is modelled by the phenomenological Gilbert damping factor. We meet the challenge
to understand the microscopic origin of energy and angular momentum dissipation which are
essential to interpret a damping in the ultrafast regime and to bridge the gap between the ultrafast
und long time scale. Varying the excitation strength of the pump pulse leads to a reinforced
effectiveness of EY spin-flip. In that case the introduced damping from [3] has to be modified.
[1] M. Cinchetti et al., Phys. Rev. Lett. 97, 177201 (2006)
[2] J.-P. Wüstenberg et al., J. Magn. Magn. Mat. 316, 411 (2007)
[3] B. Koopmans et al., Phys. Rev. Lett. 95, 267207 (2005)
41

Spin-dependent dynamics and ultrafast magnetization
Talk Tuesday 11:00
Femtosecond electron localization and transfer of angular momentum in
ferromagnetic Ni and Gd
HERMANN A. DÜRR 1 , NIKO PONTIUS 1 , CHRISTIAN STAMM 1 , TORSTEN KACHEL 1 , MARKO
WIETSTRUK 1 , WOLFGANG EBERHARDT 1 , CORNELIUS GAHL 2 , MARTIN WEINELT 2 ,
ALEXEY MELNIKOV 3 , MUHAMMAD SULTAN 3 , and UWE BOVENSIEPEN 3
1 BESSY, Berlin, Germany
2 Max-Born-Institut, Berlin, Germany
3 Freie Universität Berlin, Berlin, Germany
hermann.duerr@bessy.de
When the electronic system of a solid is rapidly heated by absorbing a femtosecond optical laser
pulse it takes time to re-establish thermal equilibrium. This timescale is ultimately determined
by energy transfer from the electronic system to the lattice. For ferromagnets this process can
also lead to an ultrafast quenching of the ferromagnetic order. Angular momentum conservation
dictates that an exchange of spin angular momentum with a reservoir such as the lattice should
occur. So far real time studies of these processes were limited to the use of femtosecond laser
pump-probe spectroscopy. The use of fs soft x-ray pulses allows us to element specifically probe
the magnetic valence shell and separate spin and orbital component of the magnetic moment. We
will demonstrate for Gd and Ni, prototypical localized and itinerant ferromagnets, respectively,
how novel channels for angular momentum dissipation to the lattice can be opened by fs laser
excitation. Fs time-resolved x-ray absorption spectroscopy of itinerant d-electrons shows an unexpected
increase in valence electron localization possibly providing the driving force behind fs
spin-lattice relaxation.
42

Spin-dependent dynamics and ultrafast magnetization
Extended talk Tuesday 11:20
Non-equilibrium surface and bulk spin-dynamics at Gd(0001)
ALEXEY MELNIKOV 1 , HELENA PRIMA-GARCIA 2 , MARKO WIETSTRUK 3 , MUHAMMAD
SULTAN 1 , TORSTEN KACHEL 3 , NIKO PONTIUS 3 , CHRISTIAN STAMM 3 , ROLAND SCHMIDT 2 ,
MARTIN LISOWSKI 1 , TANJA GIESSEL 2 , RAMONA WEBER 2 , CORNELIUS GAHL 2 , N.
BULGAKOVA 4 , T. WEHLING 5 , UWE BOVENSIEPEN 1 , MARTIN WEINELT 1,2 , HERMANN A.
DÜRR 3 , A. LICHTENSTEIN 5 , M. KATSNELSON 6 , and WOLFGANG EBERHARDT 3
1 Freie Universität Berlin, Fachbereich Physik, Berlin, Germany
2 Max-Born-Institut, Berlin, Germany
3 BESSY GmbH, Berlin, Germany
4 Institute of Thermophysics SB RAS, Novosibirsk, Russia
5 Institut für Theoretische Physik, Universität Hamburg, Hamburg, Germany
6 Institute for Molecules and Materials, Radboud University of Nijmegen, Netherlands
alexey.melnikov@physik.fu-berlin.de
In ferromagnetic metals the charge, lattice, and spin degrees of freedom are coupled. The respective
coupling strengths result in characteristic timescales on which excitations of one particular
subsystem interact and equilibrate with the remaining subsystems. To elucidate these interaction
mechanisms and their timescales at the Gd(0001) surface and in Gd bulk we investigate the
ultrafast spin dynamics after excitation by intense infrared optical pulses. We use several complementary
time-resolved methods: (i) the magnetic linear dichroism in photoemission from the
4f core-level measured at Gd(0001) at BESSY employing 1.55 eV, 100 fs laser pump and 60 eV,
50 ps synchrotron-radiation probe-pulses [1]; (ii) X-ray magnetic circular dichroism experiments
at Gd M4,5 absorption edges measured at the fs-slicing facility at BESSY using polycrystalline
Gd films; (iii) MOKE investigated at Gd(0001) using 1.55 eV, 35 fs laser pump and probe pulses
with simultaneous detection of (iv) second harmonic generation. The last method is sensitive to
the transient surface magnetization MS while techniques (i)-(iii) monitor the transient bulk magnetization
MB. From the similarity of the results of methods (i)-(iii), we conclude that MOKE
also monitors the dynamics of 4f spins. MB decreases in 2 steps at 1 ps and 50 ps time scales due
to interaction of 4f spins with hot electrons and lattice, respectively. A break-down of MS occurs
during laser excitation on a 50 fs time scale followed by further decrease induced by hot electrons
on a 1 ps time scale. The former break-down is caused by an effective spin-flip during the
re-screening of photo-holes in the surface layer [2] leading to a 5 times larger ultrafast decrease
of MS in comparison to MB. The equilibration of MS and MB takes about 200 ps, which can be
explained by fast (on a scale of 1 ps) increase of surface to second layer distance caused by the
spin-flip in the surface atomic plane [2]. Thereafter the system is trapped in a meta-stable state
and slowly relaxes to the ground state by thermal fluctuations. The related microscopic processes
will be discussed.
[1] A. Melnikov et al., Phys. Rev. Lett. 100, 107202 (2008)
[2] A. Melnikov et al., submitted to Journal of Physics D
43

Spin-dependent dynamics and ultrafast magnetization
Extended talk Tuesday 11:50
Image-potential states – Observer states for ultrafast magnetization
dynamics
ANKE B. SCHMIDT 1 , MARTIN PICKEL 2 , MARKUS DONATH 1 , and MARTIN WEINELT 2
1 Physikalisches Institut, Westfälische Wilhelms-Universität Münster, Germany
2 Max-Born-Institut Berlin and Fachbereich Physik, Freie Universität Berlin, Germany
anke.schmidt@uni-muenster.de
Recent experiments [1] demonstrate that significant demagnetization of 3d ferromagnetic thin
films upon laser excitation can be achieved within a few hundred femtoseconds. Within this timescale,
the excited electronic system and the underlying lattice are not in equilibrium and it
seems that the transient hot electron population is responsible for the change of the magnetisation.
Usually, spin-orbit coupling is responsible for the transfer of angular momentum from
the spin system to the lattice upon reversal of the magnetization but for the itinerant ferromagnets
this process is believed to occur on the timescale of the ensemble-averaged spin-lattice
relaxation-time of some picoseconds. It therefore remains controversial to date which microscopic
processes are fast enough to be involved in this new phenomenon of femtomagnetism. We
have followed two separate approaches to unravel this mystery, both of which employ the imagepotential
electron on ultrathin iron and cobalt films on Cu(100) as “test charge” or “observer
state”:
To meet the challenge of direct experimental access to the spin-dependent relaxation processes
of low-energy electrons in d band ferromagnets, we combined time-, angle- and energy-resolved
bichromatic two-photon photoemission (2PPE) with spin-resolved electron detection. We could
thus identify several instances where electron-magnon scattering strongly contributes to the femtosecond
electron dynamics in ferromagnetic films. We prove in our experiments directly in the
time domain that electron-magnon scattering is ultrafast. Thus magnon emission does not constitute
a bottleneck for the speed of magnetic switching and may very well be a microscopic process
participating in femtomagnetism.
A net demagnetization of the electronic system can be caused by Elliot-Yafet type electronphonon
scattering, i.e. scattering between spin-orbit coupled electronic states, because only in the
presence of spin-orbit coupling can electrons undergo a spin flip. Though the average spin-flip
probability in the 3d ferromagnets is about two orders of magnitude too low to explain femtosecond
demagnetization, we know from aluminium that the spin-flip probability increases significantly
at spin-orbit hybridization points in the band structure [2]. The observation of magnetic
linear dichroism in 2PPE was used to identify such spin “hot-spots” close to the Fermi level in
the band structure of ferromagnetic fcc cobalt films.
[1] E. Beaurepaire et al., Phys. Rev. Lett. 76, 4250 (1996)
[2] J. Fabian and S. D. Sarma, Phys. Rev. Lett. 81, 5624 (1998); ibid. 83, 1211 (1999)
44

45
Notes

Wednesday morning
Attosecond physics and ultrafast X-ray pulses
9:00 Attosecond Physics
Ferenz Krausz
9:40 XUV pump-probe spectroscopies - new tools to study ultrafast dynamics
Wilfried Wurth
11:00 Extreme ultraviolet photoelectron emission spectroscopy reveals dynamics of superheated
hydrogen-bound metastable phases
O. Link, E. Vöhringer-Martinez, E. Lugovoj, Y. Liu, K. Siefermann, M. Faubel, H.
Grubmüller, Bernd Abel
11:20 Direct measurement of core-level relaxation dynamics on a surface-adsorbate system
Margaret Murnane, Henry Kapteyn
12:00 Ultrafast surface dynamics probed by time- and angle-resolved photoemission using femtosecond
light pulses in the visible and XUV regime
Stefan Mathias, Luis Miaja-Avila, Andreas Ruffing, Martin Wiesenmayer, Frederik
Deicke, Henry Kapteyn, Margaret Murnane, Martin Aeschlimann, Michael Bauer
12:20 Direct measurement of core-level relaxation dynamics on a surface-adsorbate system
Luis Miaja-Avila, Guido Saathoff, Stefan Mathias, Jing Yin, Chan La-o-vorakiat, Michael
Bauer, Martin Aeschlimann, Margaret Murnane, Henry Kapteyn
12:40 Chirped-pulse two-photon photoemission from Cu(111) and Cs/Cu(111): experiment and
theory
Michael Bauer, F. Steeb, S. Mathias, A. Fischer, M. Aeschlimann, J.-P. Gauyacq
13:00 Break
13:20 Lunch
46

Advances in ultrafast surface spectroscopies
Invited talk Wednesday 9:00
Attosecond Physics
FERENZ KRAUSZ
Max-Planck-Institut für Quantenoptik, Garching, Ludwig-Maximilians-Universität München,
Germany
ferenc.krausz@mpq.mpg.de
Fundamental processes in atoms, molecules, as well as condensed matter are triggered or mediated
by the motion of electrons inside or between atoms. Electronic dynamics on atomic length
scales tends to unfold within tens to thousands of attoseconds (1 attosecond [as] = 10 −18 s). Recent
breakthroughs in laser science are now opening the door to watching and controlling these
hitherto inaccessible microscopic dynamics.
The key to accessing the attosecond time domain is the control of the electric field of (visible)
light, which varies its strength and direction within less than a femtosecond (1 femtosecond =
1000 attoseconds). Atoms exposed to a few oscillations cycles of intense laser light are able to
emit a single extreme ultraviolet (xuv) burst lasting less than one femtosecond [1,2]. Full control
of the evolution of the electromagnetic field in laser pulses comprising a few wave cycles [3] have
recently allowed the reproducible generation and measurement of isolated sub-femtosecond
xuv pulses [4], demonstrating the control of microscopic processes (electron motion and photon
emission) on an attosecond time scale. These tools have enabled us to visualize the oscillating
electric field of visible light with an attosecond “oscilloscope” [5], to control and probe singleand
multi-electron dynamics in atoms [6,7], molecules [8] and solids [9]. Recent experiments
indicate the feasibility of extending to frontiers of attosecond metrology towards kiloelectronvolt
photon energies [10], Megaelectronvolt electron energies [11], and a temporal resolution
approaching the atomic unit of time (∼ 24 as) [12].
[1] M. Hentschel et al., Nature 414, 509 (2001)
[2] R. Kienberger et al., Science 291, 1923 (2001)
[3] A. Baltuska et al., Nature 421, 611 (2003)
[4] R. Kienberger et al., Nature 427, 817 (2004); E. Goulielmakis et al., Science 317, 769 (2007)
[5] E. Goulielmakis et al., Science 305, 1267 (2004)
[6] M. Drescher et al., Nature 419, 803 (2002)
[7] M. Uiberacker et al., Nature 446, 627 (2007)
[8] M. Kling et al., Science 312, 246 (2006)
[9] A. Cavalieri et al., Nature 449, 1029 (2007)
[10] J. Seres et al, Nature 433, 596 (2005)
[11] L. Veisz et al., submitted for publication (2008)
[12] E. Goulielmakis et al., submitted for publication (2008)
47

Advances in ultrafast surface spectroscopies
Invited Wednesday 9:40
XUV pump-probe spectroscopies - new tools to study ultrafast dynamics
WILFRIED WURTH
Department Physik, University of Hamburg, Germany
wilfried.wurth@desy.de
To investigate ultrafast electron dynamics and atomic motion in real-time is essential for a fundamental
understanding of complex wave packet evolution in materials. As ideal tools for this
type of investigation one can envision time-resolved spectroscopic techniques in the XUV or soft
x-ray regime using femtosecond pulses. Tools such as angle-resolved photoemission (ARPES),
electron spectroscopy for chemical analysis (ESCA), x-ray absorption or emission spectroscopy
have proven to be extremely useful to study the electronic structure of complex materials in a
static mode. Powerful XUV or soft x-ray sources delivering ultrashort pulses will enable us to
obtain element-specific information on dynamic changes in the local electronic structure.
With the Free-Electron Laser in Hamburg (FLASH) a unique source for femtosecond XUVpulses
with unprecedented brightness is operational since 2005 and a number of pioneering
experiments have been performed with this source during the first user runs. In the talk I will
review some of these experiments and present some ideas how femtosecond x-ray pulses from
free-electron lasers can be used to study dynamic processes at surfaces and interfaces. I will
show first examples for time-resolved experiments performed at FLASH including the investigation
of XUV induced changes in optical reflectivity [1] as well as time-resolved photoelectron
spectroscopy [2] and discuss implications for future experiments.
[1] C. Gahl et al., Nature Photonics 2, 165 (2008)
[2] A. Pietzsch et al., New Journal of Physics 10, 033004 (2008)
48

Advances in ultrafast surface spectroscopies
Talk Wednesday 11:00
Extreme ultraviolet photoelectron emission spectroscopy reveals dynamics
of superheated hydrogen-bound metastable phases
O. LINK 1 , E. VÖHRINGER-MARTINEZ 2 , E. LUGOVOJ 1 , Y. LIU 1 , K. SIEFERMANN 1 , M.
FAUBEL 3 , H. GRUBMÜLLER 2 , and BERND ABEL 1,2
1 Institut für Physikalische Chemie der Universität Göttingen, Tammannstrasse 6, 37077
Göttingen, Germany
2 MPI für biophysikalische Chemie, Am Fassberg 11, 37077 Göttingen, Germany
3 MPI für Dynamik und Selbstorganisation, Bunsenstrasse 10, 37073 Göttingen, Germany
babel@gwdg.de
Water and other hydrogen-bonded liquids can be heated significantly above their boiling point
due to intrinsic energy barriers predicted by homogeneous nucleation theory. There has been vivid
speculation and research about the question how much water and hydrogen bonded liquids
can be heated above their boiling point eventually defining their metastable and unstable phases
and timescales of their decay. Obviously, hydrogen bond energetics and dynamics as well as correlated
intrinsic barriers ultimately govern the timescale and dynamics of the phase transition or
the phase evolution event. Here we show that the phase evolution in extreme states of laser-heated
water and methanol are different and can be probed near liquid jet interfaces via a novel ultrafast
liquid phase photoelectron spectroscopy technique. Molecular dynamics calculations helped to
understand the experimental observables, the different overall hydrogen bond and phase evolution
dynamics for superheated and supercritical phases. When comparing supercritical water and
methanol we find that a remaining entropic barrier originating from the different hydrogen bond
dynamics appears to dynamically constrain the phase evolution of methanol as opposed to water.
49

Advances in ultrafast surface spectroscopies
Invited talk Wednesday 11:20
Direct measurement of core-level relaxation dynamics on a
surface-adsorbate system
MARGARET MURNANE and HENRY KAPTEYN
JILA, University of Colorado, Boulder, CO, USA
murnane@colorado.edu
Extreme nonlinear optical techniques make it possible to upconvert visible laser light into coherent
x-rays using the process of high-order harmonic generation (HHG). In HHG, the most
loosely bound electron is ripped from an atom or molecule by a strong laser field. Once free, the
electron follows a trajectory controlled by the laser field, first moving away from the parent ion
and then reversing its motion as the laser field oscillates in time. Upon returning to the vicinity
of its parent ion, this electron has some probability of recombining with it and giving up its
excess kinetic energy as a high-energy photon. Several remarkable scientific and technological
opportunities have emerged as a result of this strong field process, including controlling electron
rescattering in order to manipulate electrons on attosecond timescales,[1] using the rescattering
electrons as a probe of molecular structure and dynamics,[2] and using the ultrashort duration
of the generated x-rays as a probe of complex electron dynamics in molecules and surfaces.[3]
New coherent imaging techniques also enable high resolution, large depth of field imaging of
thick samples.[4] In this talk we will present new results that probe and image complex, highlyexcited,
dynamics in molecules and surfaces.
Fig. 1 Measuring electron coupling between an adsorbate and a surface. (Left) Ultrafast EUV and IR
pulses are focused into a Xe/Pt(111) surface. An electron from the Xe N4 (4d) shell is ejected by the EUV,
followed by filling of the core-hole by an O2,3 (5p) shell electron and ejection of a secondary (Auger)
electron from the O2,3 shell. (Right) Measuring the inherent lifetime of the Xe 4d core-hole, indicating a
lifetime of 7.1 ± 1.1 fs.
[1] H. C. Kapteyn, O. Cohen, I. Christov, and M. M. Murnane, Science 317, 775 (2007)
[2] E. Gagnon et al., Science 317, 1374 (2007); X. Zhou et al., Phys. Rev. Lett. 100, 073902
(2008)
[3] L. Miava et al., Phys. Rev. Lett. 97, 113604 (2006); L. Miava et al., submitted (2008)
[4] R. Sandberg et al., Proc. Nat. Acad. Sci. 105, 24 (2008); R. Sandberg et al., Phys. Rev. Lett.
99, 098103 (2007)
50

Advances in ultrafast surface spectroscopies
Talk Wednesday 12:00
Ultrafast surface dynamics probed by time- and angle-resolved
photoemission using femtosecond light pulses in the visible and XUV
regime
STEFAN MATHIAS 1 , LUIS MIAJA-AVILA 3 , ANDREAS RUFFING 1 , MARTIN WIESENMAYER 2 ,
FREDERIK DEICKE 1 , HENRY KAPTEYN 3 , MARGARET MURNANE 3 , MARTIN
AESCHLIMANN 1 , and MICHAEL BAUER 2
1 Department of Physics, TU Kaiserslautern, 67663 Kaiserslautern
2 IEAP, Christian-Albrechts-Universität zu Kiel, D-24908 Kiel, Germany
3 JILA, University of Colorado, Colorado 80309-0440, USA
SMathias@gmx.de
Angle resolved photoelectron spectroscopy (ARPES) has emerged as a leading technique in
identifying static key properties of complex systems such as the electronic band structure of
adsorbed molecules, ultrathin quantum-well films or high temperature superconductors. Our
goal is to combine in an efficient manner the ARPES technique and femtosecond time-resolved
spectroscopy by using a two-dimensional analyzer for parallel energy (E) and momentum (k||)
detection.
In a first example we present and discuss time- and angle-resolved two photon photoemission
(TAR-2PPE) data of low-dimensional metallic quantum wells (QW). These systems exhibit
interesting characteristics in their electronic band structure, which potentially can affect the
excited state lifetime in specific areas in momentum space. This includes e.g. avoided crossings
of bands, k-localized band gaps or distortions in the band structure due to interaction with the
substrate. Our results of Pb and Bi QWs proof that the TAR-2PPE technique is advantageous for
mapping the interplay between the momentum dependent band structure characteristics and the
hot electron lifetime (see figure).
Furthermore, a time-resolved ARPES scheme using a femtosecond high-harmonic generation
(HHG) light source has been realized. First ARPES spectra recorded with ultra short photon
pulses of an energy of 42 eV will be presented, illustrating the potential of this technique for real
time investigations of ultrafast surface dynamics [1].
[1] S. Mathias, L. Miaja-Avila, M. Murnane, H. Kapteyn, M. Aeschlimann, and M. Bauer, Rev.
Sci. Instrum. 78, 083105 (2007)
51

Advances in ultrafast surface spectroscopies
Talk Wednesday 12:20
Direct measurement of core-level relaxation dynamics on a
surface-adsorbate system
LUIS MIAJA-AVILA 1 , GUIDO SAATHOFF 1 , STEFAN MATHIAS 2 , JING YIN 1 , CHAN
LA-O-VORAKIAT 1 , MICHAEL BAUER 3 , MARTIN AESCHLIMANN 2 , MARGARET MURNANE 1 ,
and HENRY KAPTEYN 1
1 JILA, University of Colorado, Boulder, USA
2 TU Kaiserslautern, Kaiserslautern, Germany
3 Christian-Albrechts-Universitat zu Kiel, Kiel, Germany
miajaavi@colorado.edu
Applying laser-assisted techniques to solid surfaces and, in particular, surface-adsorbate systems
would open a new route towards understanding the fundamental steps in surface chemistry. Here,
we place Xe atoms on a surface, and directly measure the time it takes for an electron to fill a
core hole generated in the Xe adsorbate by a soft-x-ray.
In the presence of the IR field, the Xe/Pt(111) photoemission spectrum should be modified by the
appearance of sidebands on the characteristic features of the spectrum i.e. the Pt d-band structure
near the Fermi edge (Fig. 1a), the Auger NOO peaks (Fig. 1b), and the Xe 4d core hole peaks.
The time evolution of the sideband height for the Pt d-band electrons corresponds to the cross
correlation between the SXR and the IR pulses. In contrast, the Auger electron sideband height
trace is clearly shifted by 6 fs with respect to time-zero. By fitting the Auger sideband height
with the convolution of a decaying exponential with the cross correlation at the Pt d-band peak,
we obtain a core-hole lifetime of 7.1 ± 1.1 fs.
We report the first time domain measurement of a core-hole lifetime on a adsorbate-substrate
system [1]. Our measurements show that time resolved measurements are possible that can definitively
identify the nature of spectral broadening in complex systems.
a) 1600
Counts
1400
1200
1000
800
600
400
200
0
76
SXR+IR
SXR only
fit
78
Pt d-band
80 82 84
Electron energy (eV)
86
√ ⎯⎯
2π σ f(E-E0 )
0.8
0.6
0.4
0.2
0.0
Extracted LAPE
sidebands
-4 0 4
E-E 0 (eV)
[1] L. Miaja-Avila et al., submitted (2008)
88
90
b) 4000
Counts
52
3500
3000
2500
2000
1500
34
SXR only
fit
} SXR+IR
36
Xe NOO Auger electrons
√ ⎯⎯
2π σ f(E-E0 )
38
40
42
Electron energy (eV)
0.8
0.6
0.4
0.2
0.0
Extracted LAAD
sidebands
-4 0 4
E-E 0 (eV)
44
46

Advances in ultrafast surface spectroscopies
Talk Wednesday 12:40
Chirped-pulse two-photon photoemission from Cu(111) and Cs/Cu(111):
experiment and theory
MICHAEL BAUER 1 , FELIX STEEB 2 , STEFAN MATHIAS 2 , ALEXANDER FISCHER 2 , MARTIN
AESCHLIMANN 2 , and JEAN-PIERRE GAUYACQ 3
1 IEAP, Sektion Physik, Christian-Albrechts-Universität zu Kiel, D-24908 Kiel, Germany
2 Department of Physics, TU Kaiserslautern, 67663 Kaiserslautern, Germany
3 Laboratoire des Collisions Atomiques et Moléculaires, Unité Mixte de Recherche
CNRS-Université Paris Sud UMR 8625, Bât 351, Université Paris-Sud, 91405 Orsay Cedex,
France
bauer@physik.uni-kiel.de
In the study of ultrafast processes at surfaces using femtosecond light sources the effect of the
spectral phase of the excitation pulse has been considered only in a few numbers of publications,
yet [1,2,3]. For instance, Petek and coworkers investigated the spectral changes in the 2PPE
signal from the Cu(111) Shockley surface state and from the excited 6s resonance state of adsorbed
Cs as induced by a controlled variation of the spectral phase of the excitation light [2,3].
In both cases the findings were attributed to the specific ultrafast dynamics of the involved intermediate
states. Here we report on an extension of these earlier studies, which considers next to
the peak position further spectral signatures such as the peak FWHM and the peak asymmetry.
Additionally we develop theoretical models, which enable us to reproduce and interpret our observations
in a quantitatively very satisfactory manner. For the 2PPE from the Cu(111) Shockley
state our model almost perfectly reproduces these spectral changes in a non-resonant excitation
scheme under consideration of the complete spectral phase of the laser pulse. The consequent
interpretation differs conceptually from the interpretation given by Petek and coworkers and will
be discussed in the presentation.
Our experimental findings for the Cs/Cu(111) system are supported by ab-initio calculations,
based on a wave-function approach [4]. The refined model allows us to quantitatively isolate the
effects arising from the ultrafast dynamics associated with the adsorbate motion. It furthermore
enables us to separate the effects due to a pure lengthening of the light pulse and effects directly
related to the phase modulation.
The presented results and the earlier studies by Petek and coworkers show that chirped pulse
2PPE measurements supported by adequate theoretical models can be useful in studying surface
dynamics complementary to conventional 2PPE spectroscopy and time-resolved 2PPE.
[1] H. Petek et al., Phys. Rev. Lett. 79, 4649 (1997)
[2] H. Petek et al., J. Phys. Chem. A 104, 10234 (2000)
[3] M. Merschdorf et al., Phys. Rev. B 70, 193401 (2004)
[4] J. P. Gauyacq and A. K. Kazansky, Phys.Rev. B 72, 045418 (2005)
53

Wednesday afternoon
Vibrational energy transfer and wave-packet dynamics
14:40 Excitation mechanism and decay dynamics of coherent surface phonons at metal surfaces
adsorbed by alkali-metal atoms
Kazuya Watanabe, Yoshiyasu Matsumoto
15:20 Molecular response of D2O on Ru(001) after femtosecond-laser excitation
Juraj Bdˇzoch, Philipp Giese, Martin Wolf, Christian Frischkorn
15:40 Neutral D atom desorption from graphite by visible and XUV femtosecond laser pulses
Robert Frigge, Tim Hoger, Björn Siemer, Carsten Thewes, Marco Rutkowski, Stefan
Düsterer, Helmut Zacharias
16:00 Non-adiabatic electron-phonon decoupling in graphite
Kunie Ishioka, L. Wirtz, A. Rubio, H. Petek
16:20 Ultrafast spectroscopy of coherent optical phonons in Ge2Sb2Te5 superlattics
Yoshinobu Miyamoto, Muneaki Hase, Junji Tominaga
16:40 Coffee break
17:20 Ultrafast electron dynamics of a single metal nanostructure
Alexandria Anderson, Markus B. Raschke
17:50 Coherent LO phonon self-energy renormalization under high photoexcited carrier densities
in Si
Anca-Monia Constantinescu, Muneaki Hase, Masahiro Kitajima, Hrvoje Petek
18:20 Ultrafast vibrational dynamics of interfacial water
Mischa Bonn, Maria Sovago, Avishek Ghosh, Jens Bredenbeck, R. Kramer Campen
19:00 Beer and Snacks
19:30 Poster session
54

Wave-packet dynamics
Invited talk Wednesday 14:40
Excitation mechanism and decay dynamics of coherent surface phonons at
metal surfaces adsorbed by alkali-metal atoms
KAZUYA WATANABE and YOSHIYASU MATSUMOTO
Department of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502,
Japan
matsumoto@kuchem.kyoto-u.ac.jp
When an impulsive force with duration shorter than the oscillation period of a lattice perturbs
a solid, the constituent atoms respond by oscillating coherently with amplitude proportional to
the force. For bulk materials and surfaces the impulsive force and the ensuing coherent phonon
dynamics can be applied and probed by ultrafast laser irradiation. [1]
We have studied excitation mechanisms and coherent phonon dynamics at alkali-metal covered
metal surfaces. Near infrared or visible fs laser pulses impulsively excite surface phonons, including
the stretching vibrational modes of alkali-metal atoms, and subsequent nuclear wavepacket
motions are monitored via intensity modulations of the second harmonic (SH) of a time-delayed
probe pulse as a function of pump-probe delay, td.
Coherent nuclear motion at surfaces can be driven by either the surface or substrate electronic
excitation. To clarify the excitation mechanism, we measured the photon energy dependence
of the initial phonon amplitude for Na/Cu(111). [2] A steep increase in the amplitude in the
range between 2.0 and 2.5 eV, which mimics the substrate absorbance, is associated with the
electronic transitions from the d-band of copper. This indicates that substrate electronic excitation
is responsible for the creation of coherent surface phonons.
For comparison, we replaced Na with Cs and pumped the copper surface with laser pulses at
1.55 eV. The absorbance of bulk copper at 1.55 eV is substantially smaller than at around 2.2
eV. Nonetheless, we observed clearly that the stretching mode of Cs on Cu(111) is coherently
excited. Since the duration of pump pulses used in the measurements was shortened (30 fs)
by using combination of Kr gas and chirped mirrors, electronic and phononic contributions to
transient SH signals at td ∼ 0 were clearly resolved. The phonon amplitude increases with pump
laser fluence, but tends to saturate at high laser fluences. In particular, the decay rate of the
coherent phonons is independent of the pump fluence. This behavior is very different from that
of Cs/Pt(111); the decay rate strongly increases with pump fluence. [3] We discuss the excitation
mechanisms and decay dynamics of the coherent phonons at the metal surfaces.
References
[1] Y. Matsumoto and K. Watanabe, Chem. Rev. 106, 4234 (2006)
[2] M. Fuyuki, K. Watanabe, D. Ino, H. Petek, and Y. Matsumoto, Phys. Rev. B 76, 115427
(2007)
[3] K. Watanabe, N. Takagi, and Y. Matsumoto, Phys. Rev. Lett. 92, 57401 (2004)
55

Laser-induced photochemical reactions
Talk Wednesday 15:20
Molecular response of D2O on Ru(001) after femtosecond-laser excitation
JURAJ BD ˇZOCH, PHILIPP GIESE, MARTIN WOLF, and CHRISTIAN FRISCHKORN
Physics Department, Freie Universität Berlin, Germany
christian.frischkorn@physik.fu-berlin.de
Both the ultrafast desorption dynamics of water molecules from thin D2O layers and the solvent
rearrangement upon electron injection into such layers on a Ru(001) surface have been studied
with surface femtochemistry techniques (such as fluence dependence and two-pulse correlation
measurements) [1] and vibrational spectroscopy, respectively. While electrons may contribute to
the energy transfer in substrate-mediated chemical reactions at surfaces and thus are inherently
associated with nonadiabatic coupling of electronic and nuclear degrees of freedom, electrons
as excess charges in polar solvents result in molecular motion within the solvent to stabilize
the new charge distribution [2]. In the former case, the D2O desorption dynamics after excitation
with 800-nm pulses from Ru(001) surface, we find evidence for a combined electron- and
phonon- driven reaction mechanism. On the other hand, if the Ru surface is excited with 266-nm
photons, excess electrons injected into the adsorbate layer induce –dependent on layer morphology
and layer thickness– drastic changes in the vibrational spectra of the OD stretch vibration
as exemplified in the Figure below.
SFG intensity [a.u.]
200
150
100
50
0
OD hydrogenbonded
2450
2500
2550
2600
crystal. ~10 BL D O,
2
unexcited
after 266-nm irradiation
free OD stretch
2650
vibrational frequency [cm -1]
[1] C. Frischkorn and M. Wolf, Chem. Rev. 106, 4207 (2006)
[2] B. C. Garret, D. A. Dixon et al., Chem. Rev. 105, 355 (2005)
56
2700
2750

Laser-induced photochemical reactions
Talk Wednesday 15:40
Neutral D atom desorption from graphite by visible and XUV femtosecond
laser pulses
ROBERT FRIGGE 1 , TIM HOGER 1 , BJÖRN SIEMER 1 , CARSTEN THEWES 1 , MARCO
RUTKOWSKI 1 , STEFAN DÜSTERER 2 , and HELMUT ZACHARIAS 1
1 Physikalisches Institut, Universität Münster, Germany
2 Hasylab, Hamburg, Germany
r.f@uni-muenster.de
The desorption of hydrogen from HOPG is an important issue in the understanding of molecular
hydrogen formation on interstellar dust particles. In so called H-I-clouds particles form areas of
higher density in which protostars develop. The rise of protostars out of H-clouds is not yet fully
understood. Surface mediated processes are involved and lead under high energy radiation to H
atoms.
This talk presents the deuterium desorption from a HOPG sample. The velocity distribution of
atomic deuterium from HOPG is examined after surface excitation with fs pulses at 400 nm using
a Ti:Sa laser system and at 32 nm using a free electron laser (FLASH). The atomic deuterium is
ionized via the 1s → 2s transition using a 2+1 REMPI detection scheme. The ionized D atoms
are detected by a time-of-flight mass spectrometer. The arrival time distribution of D atoms in
the detection volume is measured by varying the delay between the desorption and the probe
laser. The time-of-flight distributions are transfered by a Jacobi transformation into a velocity
distribution. Desorption by 400 nm pulses yields fast D atoms with an average kinetic energy of
〈Ekin, 400 nm〉 ≈ 410 meV, while desorption at 32 nm yields extremely slow atoms with an average
kinetic energy of 〈Ekin, 32 nm〉 ≈ 30 meV. The intensity dependence of the desorption rate from
the desorption laser at 400 nm is of approximately second order with a linearized desorption cross
section of about σ400 nm = 7 × 10 −21 cm 2 while the desorption cross section at 32 nm is about
σ32 nm = 1.9 × 10 −19 cm 2 . The results are discussed more generally using the two temperature
model and in light of a recent DFT calculation [1,2].
[1] L. Hornekær, E. Rauls, W. Xu, ˇZ. ˇSljivančanin, R. Otero, I. Stensgaard, E. Lægsgaard, B.
Hammer, and F. Besenbacher, Phys. Rev. Lett. 97, 186102 (2006)
[2] N. Rougeau, D. Teillet-Billy, and V. Sidis, Chem. Phys. Lett. 431, 135 (2006)
57

Wave packet dynamics
Talk Wednesday 16:00
Non-adiabatic electron-phonon decoupling in graphite
KUNIE ISHIOKA 1 , LUDGER WIRTZ 2 , ANGEL RUBIO 3 , and HRVOJE PETEK 4
1 National Institute for Materials Science, Tsukuba, Japan
2 Inst. Electronics, Microelectronics and Nanotechnology, Villeneuve d’Ascq, France
3 European Theoretical Spectroscopy Facility, Donostia, Spain
4 University of Pittsburgh, Pittsburgh, USA
ishioka.kunie@nims.go.jp
In USD5 we reported an experimental observation of the coherent in-plane (E2g2) phonon of
graphite, and of its transient frequency shift in picosecond time scale (Figure). In the present
talk, we explain the unusual phonon stiffening in terms of the light-induced electron-phonon
(e-p) decoupling [1]. The frequency of the high-energy phonon branches of graphite near the
Γ point is renormalized (softened) due the presence of Kohn anomaly, the slope of which is
proportional to the e-p interaction [2]. Our non-adiabatic DFT calculations demonstrate that,
like statically doped electrons (holes) [3], photoexcited hot electron-hole pairs cannot follow the
ionic motion adiabatically due to the quasi-2D electronic structure of graphite. This implies a
decoupling the e-p interaction and lead to a phonon stiffening without lattice deformation. After
the instantaneous (≪100 fs) stiffening, the time-dependent phonon frequency probes sensitively
the time evolution of the transient electronic occupation distributions. Our results offer a new
paradigm of e-p coupling, where non-equilibrium electrons impart exceptional properties to the
lattice.
[1] K. Ishioka et al., Phys. Rev. B 77, 121402(R) (2008)
[2] S. Piscanec et al., Phys. Rev. Lett. 93, 185503 (2004)
[3] S. Pisana et al., Nat. Mater. 6, 198 (2007)
Phonon Frequency (THz)
47.7
47.6
47.5
47.4
47.3
0
Raman frequency 47.36 THz
1
2
Time (ps)
58
3
1 mJ/cm 2
0.6 mJ/cm 2
0.2 mJ/cm 2
4

Coherent phenomena
Talk Wednesday 16:20
Ultrafast spectroscopy of coherent optical phonons in Ge2Sb2Te5
superlattics
YOSHINOBU MIYAMOTO 1 , MUNEAKI HASE 1,2 , and JUNJI TOMINAGA 3
1 Institute of Applied Physics, University of Tsukuba, Tsukuba, Japan
2 PRESTO, Japan Science and Technology Agency, Kawaguchi, Japan
3 Center for Applied Near-field Optics Research, AIST, Tsukuba, Japan
mhase@bk.tsukuba.ac.jp
One of the most common materials for optical recording media is Ge2Sb2Te5 (GST), in which
phase transition between crystalline and amorphous phases serve rewritable recording. Although
extended x-ray absorption fine structure and Raman scattering measurements have examined to
study dynamics of phase transition in GST, a time-resolved study is still very few [1]. In order
to understand and to control rapid phase change in GST, whose time scale has been believed to
be less than nanosecond, time-resolved study of phonon dynamics in GST is strongly demanded.
Moreover, a new class of semiconductor superlattices (GeTe/Sb2Te3) with three different states
have recently been proposed, which will enable us to realize reversible transition among the
three states by means of laser pulses [2]. Here, we present ultrafast dynamics of coherent optical
phonons observed in GeTe/Sb2Te3 superlattices as well as in GST films.
A reflection-type pump-probe measurements using a mode-locked Ti:sapphire laser (20 fs and
a central wavelength 850 nm) was employed at 295 K. This system enabled us to detect optical
response over 30 THz bandwidth. The average power of the pump beam was varied from 20 to
190 mW, while that of the probe beam was kept at 3 mW. The samples used were GeTe/Sb2Te3
superlattices with a period of ∼ 1 nm on Si (100) substrate, as-grown (amorphous) and annealed
(crystalline) Ge2Sb2Te5 films on Si (100) substrate with a thickness of ∼ 18 nm.
The time-resolved transient reflectivity observed in amorphous Ge2Sb2Te5 films at the highest
pump fluence, 450 µJ/cm 2 , exhibits coherent phonon oscillations with modulation of their oscillation
pattern, while that in crystalline film shows simple damped harmonic oscillation. The
difference in these two samples is clear in the corresponding Fourier transformed (FT) spectra,
where the A1 optical modes appear at 4.8 THz (amorphous Te-Te bond) and 3.7 THz (GeTe4)
in amorphous film, while only the 3.7 THz peak is observed in crystalline film, being consistent
with the pioneer work [1]. On the other hands, the coherent optical phonons in GeTe/Sb2Te3
superlattices exhibit significant shift of their frequency relative to the GST film. The shift of the
phonon frequency observed in superlattices can be attributed to confinement of the optical modes
in each layers.
[1] M. Först et al., Appl. Phys. Lett. 77, 1964 (2000)
[2] T. C. Chong et al., Phys. Rev. Lett. 100, 136101 (2008)
59

Coherent phenomena
Extended talk Wednesday 17:20
Ultrafast electron dynamics of a single metal nanostructure
ALEXANDRIA ANDERSON and MARKUS B. RASCHKE
Department of Chemistry, University of Washington, Seattle, WA 98103, USA
raschke@chem.washington.edu
The ultrafast electronic dephasing in metal nanostructures is determined by their size, shape,
and chemical environment. To discriminate different relaxation channels, probing on the single
particle level is particularly desirable avoiding effects due to the heterogeneity of the ensemble
[1]. Here, we study the phase decoherence of individual free standing gold nanotips by secondharmonic
interferometric autocorrelation using sub-10 fs Ti:S fundamental excitation. In sagittal
excitation and 90 ◦ SHG scattering detection this gives access to the pure local surface SHG response
associated with the axial plasmon resonance of the structure [2]. The coherent dynamics
observed can be described by a plasmon resonant one-photon transition with T2 ∼ 3 − 5 fs and
a two-photon transition with a decoherence of T2 ∼ 30 − 50 fs that can be attributed to the
interband excitation of Au (see Fig. 1), with the range in values depending on tip geometry. The
deconvolution of the individual resonant contributions and the driving field transient is obtained
from the numerical solution of the Bloch equations for a three level system [3].
Fig. 1: Second-harmonic interferometric autocorrelation of the ultrashort pulse interaction with an individual
gold nanostructure. Inset: spectrally resolved data for a different Au nanotip.
[1] M. W. Klein, T. Tritschler, M. Wegener, and S. Linden, Phys. Rev. B 72, 115113 (2005)
[2] C. C. Neacsu, G. A. Reider, and M. B. Raschke, Phys. Rev. B 71, 201402 (2005)
[3] M. J. Weida, S. Ogawa, H. Nagano, and H. Petek, J. Opt. Soc. Am. B 17 1443 (2000)
60

Coherent phenomena
Extended talk Wednesday 17:50
Coherent LO phonon self-energy renormalization under high photoexcited
carrier densities in Si
ANCA-MONIA CONSTANTINESCU 1 , MUNEAKI HASE 1 , MASAHIRO KITAJIMA 2 , and HRVOJE
PETEK 3
1 University of Pittsburgh, Pittsburgh, PA,USA
2 University of Tsukuba, Japan and PRESTO-JST, Japan
3 National Institute for Material Science, Tsukuba, Japan and NDA, Japan
anc2598@pitt.edu
The study of hot carrier-phonon interaction is motivated by their influence on optical and electrical
properties of semiconductors. Elucidating the dynamics of electrons in the presence of the
phonon system can help in improving the performances of small size electronic devices. Following
high-density (10 19 – 10 20 carriers/cm 3 ) photoexcitation of Si(001) with 10 fs duration, 400 nm
laser pulses, the complex self-energy (i.e. the frequency and decay rate) of coherent zone-center
LO phonon renormalizes due to the deformation potential interaction with the photogenerated
non-equilibrium plasma. First systematic studies of the influence of doping carriers on the Raman
lines of Si were done by Cerdeira et al. [1] with the conclusion that both the frequency and
dephasing time shift linearly with doping concentration, and the strength of the shift depends on
the doping type.
We extract the time dependent LO phonon frequency and dephasing time from the transient
electro-optic reflectivity of variously doped Si(100). We measure the coherent oscillations in the
transient reflectivity signal over a delay time of 5 ps. Varying the pump power from 5 to 50 mW,
we observe that the electronic softening of the lattice, translated in LO phonon frequency change,
and the dephasing time of the phonon depend on the initial photoexcited carrier density, as well
as on the doping concentration and type of the sample.
We conclude that photodoping near the threshold of thermal melting induces a nonlinear shift
of both the frequency and dephasing time of the LO phonon. The lattice softens in about 0.5 ps
after excitation, but recovers much slower, reflecting the time frame needed by the photoexcited
carriers to undergo thermalization, interband and intraband transitions and, ultimately, diffusion
towards bulk.
[1] F. Cerdeira and M. Cardona, Phys. Rev. B 5, 1440 (1972)
61

Vibrational energy transfer
Invited talk Wednesday 18:20
Ultrafast vibrational dynamics of interfacial water
MISCHA BONN, MARIA SOVAGO, AVISHEK GHOSH, JENS BREDENBECK, and R. KRAMER
CAMPEN
FOM-Institute for Atomic and Molecular Physics AMOLF, Kruislaan 407, 1098 SJ Amsterdam,
The Netherlands
bonn@amolf.nl
Interfacial water is of importance for a variety of disciplines including electrochemistry, (photo-)
catalysis and biology. Water interfaces are characterized by the interruption of the bulk hydrogen
bonded network, which gives interfacial water its unique properties (e.g. high surface tension).
When a water OH group forms a hydrogen bond, the OH stretch frequency of this group decreases
by an amount determined by the H-bond strength. As such, the frequency and lineshape of
the O-H stretch vibration of interfacial water – determined, for example, using surface-specific
Vibrational Sum-Frequency Generation (VSFG) Spectroscopy – provides a sensitive marker of
the local environment of interfacial water molecules.
We report a frequency- and femtosecond time-resolved study of water at various interfaces using
VSFG. In the time-resolved measurements, the O-H stretch vibrational lifetime of hydrogenbonded
interfacial water is determined using a novel, surface-specific 4 th -order VSFG spectroscopy.
The O-H stretch vibration of interfacial water is resonantly excited with an intense, 100 fs
infrared pulse; the vibrational relaxation dynamics are followed with femtosecond, time-resolved
VSFG spectroscopy.
Our results reveal that interfacial water is structurally more homogeneous than previously
thought. Furthermore, ultrafast exchange of vibrational energy can occur between water surface
and bulk water, but the the occurrence of ultrafast resonant vibrational energy transfer depends
critically on the details of the water interface. Finally, we demonstrate a new type of twodimensional
surface spectroscopy that allows one to follow the structural evolution of interfacial
molecular systems in real-time.
[1] M. Sovago, R. K. Campen, G. W. H. Wurpel, M. Müller, H. J. Bakker and M. Bonn, Phys.
Rev. Lett. 100 173901 (2008)
[2] M. Smits, A. Ghosh, M. Sterrer, M. Müller and M. Bonn, Phys. Rev. Lett. 98, 098302 (2007)
[3] A. Ghosh, M. Smits, J. Bredenbeck and M. Bonn, J. Am. Chem. Soc. 129, 9608 (2007)
[4] J. Bredenbeck, A. Ghosh, M. Smits and M. Bonn, J. Am. Chem. Soc. 130, 2152 (2008)
62

19:30 Wednesday poster
Poster session
W1 Ultrafast Electron Dynamics in Quantum Well States of Pb/Si(111) Investigated by Two-
Photon Photoemission
Patrick S. Kirchmann, L. Rettig, M. Wolf, U. Bovensiepen
W2 Electron confinement in Cu quantum corrals on a Cu(111) surface
Jean-Pierre Gauyacq, Sergio Díaz-Tendero, Fredrik E. Olsson, Andrei G. Borisov
W3 A time-resolved photoemission study of the TiSe2 transition metal dichalcogenide compound
Martin Wiesenmayer, S. Mathias, T. Rohwer, O. Andreyev, M. Bauer
W4 Time- and angle-resolved 2PPE study of the transition from image-potential states to resonances
Andreas Damm, Kai Schubert, Jens Güdde, Ulrich Höfer
W5 Using time-resolved surface second harmonic generation to probe interfacial electron transfer
at a semiconductor surface
William A. Tisdale, Eray S. Aydil, David J. Norris, Xiaoyang Zhu
W6 Momentum-resolved lifetime study of image potential states using a novel 500 kHz twocolor
fiber-laser based NOPA system
Klaus Duncker, Mario Kiel, Wolf Widdra
W7 Three-Photon Photoemission from Cu(001) Studied with Spin and Time Resolution
Cheng-Tien Chiang, A. Winkelmann, F. Bisio, W.-C. Lin, H. Petek, J. Kirschner
W8 Development of femtosecond X-ray diffraction
Masaki Hada, Jiro Matsuo
W9 Correlations between optically-induced nonlinear processes at metal surfaces
Francesco Bisio, A. Winkelmann, W.-C. Lin, C.-T. Chiang, M. N´yvlt, H. Petek, J. Kirschner
W10 Coherent electron dynamics in image-potential states on Ag(111) investigated with 2PPE
Manuel Marks, Christian Schwalb, Kai Schubert, Ulrich Höfer
W11 Hot Electron-induced Crystallization of Frozen Ammonia Film on Ag(111)
Hyuksang Kwon, Sunmin Ryu, Kiwook Hwang, Juyeon Park, Seong Keun Kim
W12 Photochemistry of Excitonic States of C60 Surfaces
B. Göhler, T. Hoger, A. Rosenfeldt, Helmut Zacharias
W13 Laser-Induced Magnetic Phase Transitions on FeRh Thin Films: a Time-Resolved XMCD
Study
Ilie Radu, C. Stamm, N. Pontius, T. Kachel, P. Ramm, J. U. Thiele, H. A. Dürr, C. H. Back
W14 Time-resolved and temperature dependent photoemission from a ferromagnetic h-
BN/Ni(111) surface
Dominik Leuenberger, Matthias Hengsberger, Jürg Osterwalder
W15 Spin calibration of an electron time-of-flight spin analyzer by spin-resolved photoemission
on Au(111) surface states
Céphise M. Cacho, Marco Malvestuto, Sergio Vlaic, Elaine A. Seddon, Fulvio Parmigiani
W16 Core-level shifts induced by femtosecond laser excitation
Andrea Melzer, Daniel Kampa, Jinxiong Wang, Thomas Fauster
W17 A femtosecond X-ray/optical cross-correlator: Free-electron laser X-ray pulse induced transient
optical reflectivity
C. Gahl, A. Azima, M. Beye, M. Deppe, Kristian Döbrich, U. Hasslinger, F. Hennies, A.
Melnikov, M. Nagasono, A. Pietzsch, M. Wolf, W. Wurth, A. Föhlisch
63

Electronic energy transfer W1
Poster Wednesday 19:30
Ultrafast Electron Dynamics in Quantum Well States of Pb/Si(111)
Investigated by Two-Photon Photoemission
PATRICK S. KIRCHMANN, LAURENZ RETTIG, MARTIN WOLF, and UWE BOVENSIEPEN
Fachbereich Physik, Freie Universität Berlin, Germany
patrick.kirchmann@physik.fu-berlin.de
Ultrathin metal films on semiconducting substrates present highly interesting systems to study
ultrafast electron dynamics in lowered dimensions as the electron confinement within the metal
film leads to formation of well-defined occupied and unoccupied quantum well states (QWS).
In Pb/Si(111) the quantization of the nearly-free-electron 6pz Pb band along the [111] direction
gives rise to a series of (un)occupied QWS [1] that exhibit reasonable agreement with density
functional calculations [2]. The decay of the excited electron population is monitored by
time-resolved two-photon photoemission (2PPE) directly in the time domain. The experimentally
determined electron scattering rates Γ of the two-dimensional QWS are to be compared to
Fermi-liquid theory [3,4].
We discuss exemplary Pb films where the first unoccupied state (QWS+1) is situated in the Si
band gap and the second unoccupied QWS (QWS+2) is degenerate with Si bulk bands. Here,
the electron dynamics are particularly interesting as the excited electrons in QWS+1 are confined
to the Pb film, contrary to QWS+2. The energy relaxation of QWS+1 is characterized by
a delayed rise (∼ 70 fs) and a single exponential decay (130 fs), whereas in QWS+2 a biexponential
decay featuring a fast (30 fs) and a slow (130 fs) component is encountered. The decay
dynamics of both QWS is evaluated consistently by a coupled rate equation model which takes
inter-subband scattering Γinter from the higher lying QWS+2 to QWS+1 into account. The delayed
rise in QWS+1 is explained by optical excitation of QWS+2 and inter-subband scattering
from QWS+2 into QWS+1. The observed simultaneous population decay in QWS+2 with the
build-up in QWS+1 presents a direct evidence for this description using interband scattering at
Γ −1
inter = 54(5) fs. The relaxation times reported here are at least an order of magnitude larger
than observed for QWS on metal substrates. While the depopulation studied here occurs due to
inelastic e-e scattering as the QWS+1 is within the energy gap of the substrate, in metal substrates
elastic scattering from the film to the substrate presents an efficient relaxation channel. We
will discuss that the decay rates of the two lowest QWS in Pb/Si(111) are compatible with Fermi
liquid theory if inter-subband scattering from the higher lying QWS into the lower lying QWS is
explicitly taken into account.
[1] P. S. Kirchmann et al., Phys. Rev. B 76, 075406 (2007)
[2] C. M. Wei and Y. M. Chou, Phys. Rev. B 66, 233408 (2002)
[3] D. Pines and P. Nozieres, The Theory of Quantum Liquids, (Benjamin, New York, 1966)
[4] E. V. Chulkov et al., Chem. Rev. 106, 4160 (2006)
64

W2 Electronic energy transfer
Poster Wednesday 19:30
Electron confinement in Cu quantum corrals on a Cu(111) surface
JEAN-PIERRE GAUYACQ 1,2 , SERGIO DÍAZ-TENDERO 1,2 , FREDRIK E. OLSSON 3 , and
ANDREI G. BORISOV 1,2
1 CNRS, Laboratoire des Collisions Atomiques et Moléculaires, UMR 8625,
Bâtiment 351, 91405 Orsay Cedex, France
2 Université Paris-Sud, Laboratoire des Collisions Atomiques et Moléculaires, UMR 8625,
Bâtiment 351, 91405 Orsay Cedex, France
3 Department of Applied Physics, Chalmers/Göteborg University,
S-41296 Göteborg, Sweden
jean-pierre.gauyacq@u-psud.fr
An enclosure formed by an atomic wall is able to confine the surface electronic state when deposited
on a noble metal surface [1]. These quantum corrals lead to quasi-stationary states temporarily
trapped inside the enclosure and that decay by electron scattering on the corral wall: either
transmission through the barrier or scattering into the bulk. We studied the Cu(111) surface state
continuum confined inside of a circular corral made by Cu atoms using a theoretical approach
based on both DFT (Density Functional approach) and WPP (Wave Packet Propagation)[2]. Both
the energy and lifetimes of the states confined inside the corral have been determined.
Particular emphasis has been put on the existence of sp-states localized on the Cu wall enclosing
the quantum corral. These are hybrids formed from the 4s and 4p atomic orbitals of the wall Cu
atoms. They have been observed on individual atoms and on finite Cu chains on Cu(111)[3]. On
an infinite Cu chain they form a 1D-band of states delocalized on the chain[4] and on a closed
circular wall, this 1D-band leads to quantized states. We show that the sp-states localized on the
wall mix with the confined states and deeply modify their spectrum. In particular, the decay of
the confined states is influenced by the presence of sp-states: electronic states localized on the
wall can be very efficient intermediates in the decay of the states confined inside the corral.
[1] M. F. Crommie, C. P. Lutz, and D. M. Eigler, Science 262, 218 (1993)
[2] F. E. Olsson, M. Persson, A. G. Borisov, J. P. Gauyacq, J. Lagoute, and S. Fölsch, Phys. Rev.
Lett. 93, 206803 (2004)
[3] S. Fölsch, P. Hyldgaard, R. Koch, and K. H. Ploog, Phys. Rev. Lett. 92, 056803 (2004)
[4] J. P. Gauyacq, S. Díaz-Tendero, F. E. Olsson, A. G. Borisov, at this conference
65

Electronic energy transfer W3
Poster Wednesday 19:30
A time-resolved photoemission study of the TiSe2 transition metal
dichalcogenide compound
MARTIN WIESENMAYER 1 , STEFAN MATHIAS 2 , TIMM ROHWER 1 , OLEKSIY ANDREYEV 1 ,
and MICHAEL BAUER 1
1 Institut für Experimentelle und Angewandte Physik, CAU Kiel, 24118 Kiel, Germany
2 Department of Physics, TU Kaiserslautern, 67663 Kaiserslautern, Germany
wiesenmayer@physik.uni-kiel.de
The layered transition-metal dichalcogenides (TMDC) have attracted considerable attention in
the past due to a wide range of phenomena associated with their reduced dimensionality, such as
charge density wave (CDW) instabilities and enhanced correlation effects. Recent studies of TaS2
by Perfetti et al. demonstrated, that new and interesting insights into the complex physics of these
systems can be gained by the application of the time-resolved photoemission technique [1]. In
this paper we present first time-resolved photoemission results of 1T-TiSe2, a TMDC compound
exhibiting a CDW transition at 200 K accompanied by a structural transformation.
Figure 1: Laser-induced quenching of the Se 4p band emission at varying temporal delay in time- and angular resolved 2PPE.
The excited state spectrum of TiSe2 as well as excited state lifetimes have been mapped by means
of time- and angle-resolved two-photon photoemission (2PPE). Application of polarization dependent
selection rules and comparison with band structure calculations [2] enables us to identify
element specific excited state orbitals in the photoemission spectra. For an unoccupied excited
state of Ti we measure lifetimes as short as 7 fs. We propose that next to layer internal decay
channels also inter-layer interactions may be of relevance for the efficient depopulation of this
state.
Furthermore, at temperatures above 200 K, we observe a strong quenching of the two-photon
photoemission signal from the occupied Se 4p state as the incident laser intensity is increased
[fig. 1]. In the CDW state (T < 200 K) such a quenching is completely absent. Pump-probe
experiments show that the laser-induced spectral modifications decay on a femtosecond to picosecond
time-scale indicating the involvement and relevance of hot electrons. Our results will be
discussed under consideration of the highly disputed mechanism for the CDW transition of TiSe2
[3].
[1] L. Perfetti et al., Phys. Rev. Lett. 97, 067402 (2006)
[2] A. Zunger and A. J. Freeman, Phys. Rev. B 17, 1839 (1978)
[3] see e.g.: K. Rossnagel et al., Phys. Rev. B 65, 235101 (2002) and H. Cercellier et al., Phys.
Rev. Lett. 99, 146403 (2007)
66

W4 Electronic energy transfer
Poster Wednesday 19:30
Time- and angle-resolved 2PPE study of the transition from
image-potential states to resonances
ANDREAS DAMM, KAI SCHUBERT, JENS GÜDDE, and ULRICH HÖFER
Fachbereich Physik und Zentrum für Materialwissenschaften, Philipps-Universität, D-35032
Marburg, Germany
andreas.damm@physik.uni-marburg.de
We report on the investigation of the transition from an image-potential state to a resonance by
means of time- and angle-resolved two-photon photoemission spectroscopy (2PPE). In contrast
to Cu(100) the first (n = 1) image-potential state on Cu(111) and Ag(111) is bound close to the
conduction band minimum. Due to the workfunction drop upon Ar adsorption this state becomes
a resonance on Cu(111) for Ar coverages Θ ≥ 2 ML, whereas it remains in the projected bulk
band gap on Ag(111) for coverages up to Θ = 4 ML. On Ag(111) the lifetime of the n = 1-state
shows the same exponential dependence on Ar layer thickness as on Cu(100) (Fig. 1). It rises
from 32 fs on the clean surface to about 6 ps for Ar coverages of 4 ML. The lifetime as a function
on Ar layer thickness on Cu(111) shows a strikingly different behavior as compared to Ag(111)
and Cu(100). The occurance of a kink at an Ar coverage of Θ = 2 ML correlates with the binding
energy of this state shifting into the Copper conduction band. Nevertheless, the further lifetime
dependence on layer thickness cannot be understood within a simple tunneling picture.
The use of a 2d-image-type detector makes it possible to determine the dependence of the decay
rates Γ = �/τ on parallel momentum. For each surface the change of the decay rate with kinetic
energy of motion parallel to the surface depends linearly on the decay rate at the band bottom.
The decoupling of the image-potential states by rare-gas layers leads to a pronounced decrease
of the decay rate, but reveals the same connection between the decay rate at the band bottom and
its momentum dependence.
Lifetime τ (fs)
10 4
10 3
10 2
Ar/Cu(111)
Ar/Ag(111)
Ar/Cu(100)
0 2 4 6 8 10
Ar coverage (ML)
Fig. 1: Inelastic lifetimes of the n=1 imagepotential
state as a function of Ar thickness
for Ar/Cu(111), Ar/Ag(111) and Ar/Cu(100)
(symbols). The lines for Ar/Cu(111) and
Ar/Ag(111) are to guide the eye. The data for
Ar/Cu(100) are taken from Ref. [1].
[1] W. Berthold, P. Feulner, and U. Höfer, Chem. Phys. Lett. 358, 502 (2002)
67

Electronic energy transfer W5
Poster Wednesday 19:30
Using time-resolved surface second harmonic generation to probe
interfacial electron transfer at a semiconductor surface
WILLIAM A. TISDALE, ERAY S. AYDIL, DAVID J. NORRIS, and XIAOYANG ZHU
University of Minnesota, Minneapolis, USA
tisd0012@umn.edu
Over the past decade, femtosecond transient absorption spectroscopy has been an effective tool
for studying electron injection from photoexcited molecular dyes attached to mesoporous wide
band gap semiconductor substrates (e.g. TiO2). However, the technique has been less effective in
elucidating electron transfer dynamics from photoexcited semiconductor quantum dots (QDs) attached
to similar substrates due to ambiguity in assignment of transient signals. Further, transient
absorption does not offer the sensitivity necessary for studying electron transfer at single crystal
surfaces. To overcome these limitations, we are investigating the use of time-resolved surface
second harmonic generation (TR-SHG) spectroscopy for studying interfacial electron transfer at
a semiconductor surface. For centrosymmetric substrates such as rutile TiO2, SHG originates at
the interface between the substrate and the sensitizer (dye or QD) and the second-order susceptibility
should be sensitive to transient electric fields and changes in conduction band electron
populations associated with electron transfer. We discuss recent efforts in applying TR-SHG to a
model sensitizer-semiconductor interface.
68

W6 Electronic energy transfer
Poster Wednesday 19:30
Momentum-resolved lifetime study of image potential states using a novel
500 kHz two-color fiber-laser based NOPA system
KLAUS DUNCKER, MARIO KIEL, and WOLF WIDDRA
Institute of Physics, Martin-Luther-Universität Halle-Wittenberg, Halle, Germany
klaus.duncker@physik.uni-halle.de
Ultrafast time-resolved photoemission spectroscopy in the femtosecond regime mostly relies on
titanium-sapphire based laser systems. These lasers deliver fs pulses at wavelengths around 800
nm either with high repetition rates (80 MHz) and limited puls energy (10 – 15 nJ) or with low
repetition rates (1 – 100 kHz) and high pulse energy (up to mJ). In combination with optical
parametric amplifiers (OPA) the latter provide full tunability in the visible and near IR. However
the lower repetition rates also imply lower maximum electron counting rates in photoemission
experiments and therefore longer acquisition times.
Here we present first results using a new laser source: A fiber-based oscillator and amplifier
drives simultaneously two noncollinear optical parametric amplifiers (NOPA) at repetition rates
of 200 kHz – 2 MHz [1]. In this work operation of a true two-color setup is demonstrated for
the first time at a repetition rate of 500 kHz: For the well-known image potential states at the
Ag(001) surface under ultrahigh vacuum conditions two-photon photoemission (2PPE) results
will be presented with a total time resolution of 55 fs as derived from the FWHM of the pumpprobe
crosscorrelation.
The lifetimes for the n = 1 and 2 image states have been determined as function of electron
momentum �k�. At the Γ point we find lifetimes in good agreement with the earlier study by
Shumay et al. [2]. For increasing k� from 0 to 0.4 ˚A −1 the livetime of the n = 1 state decreases
from 60 fs to 26 fs. The data are consistent with a near linear increase of the decay rate with
energy as found similarly for image potential states on Cu(001) by Berthold et al. [3].
[1] C. Homann, C. Schriever, P. Baum, and E. Riedle, Optics Express 16, 5746 (2008)
[2] I. L. Shumay, U. Höfer, Ch. Reuß, U. Thomann, W. Wallauer, and Th. Fauster, Phys. Rev. B
58, 13974 (1998)
[3] W. Berthold et al., Phys. Rev. Lett. 88, 056805 (2002)
69

Coherent phenomena W7
Poster Wednesday 19:30
Three-Photon Photoemission from Cu(001) Studied with Spin and Time
Resolution
CHENG-TIEN CHIANG 1 , AIMO WINKELMANN 1 , FRANCESCO BISIO 2 , WEN-CHIN LIN 1 ,
HRVOJE PETEK 3 , and JÜRGEN KIRSCHNER 1
1 Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, D-06120 Halle(Saale), Germany
2 CNR-INFM, Unitá di Genova, via Dodecaneso 33, I-16146 Genova, Italy
3 Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania
15260, USA
chiang@mpi-halle.de
We investigated the Cu(001) surface by angle-resolved multiphoton photoemission measurements
with spin and time resolution. A characteristic three-photon photoemission (3PPE) signal
is observed for incident photon energies near 3.0 eV, where a two-photon resonance between the
n=1 image potential (IP) state and the Cu d-bands exists [1].
Using circularly polarized light, spin-polarized electrons can be selectively excited from the Cu
d-bands into the image potential state. The angle- and photon energy dependence of the 3PPE
spin-polarization is used to sensitively study the energetic separation between the spin-orbit split
Cu d-bands and the image potential state [2].
By angle-resolved 3PPE measurements, we can clearly observe how the dispersion of the image
potential state with parallel momentum extends beyond the vacuum level. This demonstrates
directly how momentum conservation restrictions keep some photoexcited electrons trapped in
the IP state at the surface even though they nominally have enough kinetic energy to leave the
sample.
The relatively strong 3PPE signal from the two-photon excited IP state gives the unique possibility
to apply one-color interferometric time-resolved 3PPE measurements for the study of
the dynamics of the image potential state electrons. Our preliminary results indicate an IP state
lifetime near 30 fs, in good agreement with the literature.
[1] F. Bisio, M. N´yvlt, J. Franta, H. Petek, and J. Kirschner, Phys. Rev. Lett. 96, 087601 (2006)
[2] A. Winkelmann, F. Bisio, R. Ocaña, W.-C. Lin, M. N´yvlt, H. Petek, and J. Kirschner, Phys.
Rev. Lett. 98, 226601 (2007)
70

W8 Coherent phenomena
Poster Wednesday 19:30
Development of femtosecond X-ray diffraction
MASAKI HADA 1 and JIRO MATSUO 2
1 Department of Nuclear Engineering, Kyoto University, Kyoto, Japan
2 Quantum Science and Engineering Center, Kyoto University, Kyoto, Japan
hadamasaki@nucleng.kyoto-u.ac.jp
Observation of physical phenomena under energetic beam irradiation in the femtosecond time
scale has not been possible until now, but recent developments in ultrafast optical technology
allow us to measure such phenomena. Elucidating such ultrafast phenomena will lead not only to
the fundamental understanding of quantum beam science, but will also further our understanding
of physical phenomena in the uncharted nanoscale extreme conditions. We are constructing a
femtosecond X-ray diffraction system with a Ti: sapphire laser of low-power and high-repetition
rate. Ultrafast phenomena can be observed from the changes in the optical refractive index by
the traditional pump-probe measurements, but femtosecond X-ray diffraction allows us to obtain
the position of atoms directly, and to understand the movement or displacement of atoms in more
detail.
Femtosecond X-ray diffraction system is performed with a low-power (3.5 mJ/pulse) and highrepetition
(1 kHz) femtosecond laser. For a low-power laser, the pulse duration of generated
X-ray is calculated theoretically to be 100-200 fs, which is shorter than with a high-power femtosecond
laser (>100 mJ/pulse), calculated to be 300-2000 fs. Thus, the femtosecond X-ray
diffraction system using low-power and high-repetition will enable measurement of the ultrafast
phenomena with higher time resolution than the conventional femtosecond X-ray diffraction system
using high-power laser.
A mode-locked Ti: sapphire laser generated femtosecond optical pulses of about 100 fs duration,
and the optical pulses were amplified at about 3.5 mJ/pulse through a regenerative amplifier with
a repetition rate of 1 kHz. Femtosecond X-rays were generated by focusing the amplified pulses
onto a rotating copper target. The X-ray diffraction lines from Bi(0003) on sapphire substrate,
(integral diffraction intensity 28.1 cps and a sinal to background ratio of 87.5) were detected by
a CCD camera. This means that with the 300 s measurement a change of better than 2% can be
detected in the diffraction line of a Bi 100 nm thin film. The changes caused by the coherent
phonon in this diffraction line are estimated at about 3-15 %. The change of femtosecond X-ray
diffraction line obtained using femtosecond X-ray diffraction with low-power and high-repetition
laser system is expected to be clarify the Bi phonon dynamics in more detail. In the poster session,
we will present preliminary experimental data obtained with femtosecond X-ray diffraction.
71

Wave-packet dynamics W9
Poster Wednesday 19:30
Correlations between optically-induced nonlinear processes at metal
surfaces
FRANCESCO BISIO 1 , AIMO WINKELMANN 2 , WEN-CHIN LIN 2 , CHENG-TIEN CHIANG 2 ,
MIROSLAV N ´YVLT 3 , HRVOJE PETEK 4,5 , and JÜRGEN KIRSCHNER 2
1 CNISM, Sede consorziata di Genova and Dipartimento di Fisica, Genova, Italy
2 Max-Planck-Institut für Mikrostrukturphysik, Halle (Saale), Germany
3 Faculty of Mathematics and Physics, Institute of Physics, Charles University, Praha, Czech
Republic
4 Department of Physics and Astronomy, University of Pittsburgh, USA
5 Donostia International Physics Center DIPC, San Sebastian, Spain
bisio@fisica.unige.it
We have performed a combined study of second harmonic generation (SHG) and multi-photon
photoemission (mPPE) at Cu(001) surfaces as a function of the modification of the height of the
surface energy barrier EV induced by Cs adsorption. Close comparison of the mPPE spectra recorded
as a function of decreasing EV with the corresponding SHG intensity dependence allows
to interpret the optically-induced nonlinear phenomena at the surface in terms of resonant and
non-resonant electronic transitions between bulk and surface electronic states. By means of such
analysis, we obtain a marked correlation between an increase in the probability of escape into the
vacuum at the two-photon resonance of the d-band electrons and a pronounced decrease of the
SHG yield. We model this interplay between optical and photoelectric response of the material
by treating photoemission as an effective source of polarization decay in the second harmonic
generation process.
72

W10 Wave-packet dynamics
Poster Wednesday 19:30
Coherent electron dynamics in image-potential states on Ag(111)
investigated with 2PPE
MANUEL MARKS, CHRISTIAN SCHWALB, KAI SCHUBERT, and ULRICH HÖFER
Fachbereich Physik und Zentrum für Materialwissenschaften, Philipps-Universität,
Renthof 5, D-35032 Marburg, Germany
Manuel.Marks@physik.uni-marburg.de
Image-potential states are unoccupied, two dimensional states in front of metal surfaces forming
a Rydberg-series En = Evac − 0.85/(n + a) 2 converging to the vacuum energy [1]. Up to now,
the most thoroughly studied system is Cu(100). There, the vacuum level is located in the middle
of the projected gap of the bulk sp-band. The measured lifetimes were found to scale like τn ∝ n 3
as expected theoretically [2]. Recently, Borisov et al. predicted a similar n 3 -dependent lifetime
for the image-potential resonances of the (111) surfaces of Cu, Ag and Au for which the states
(n ≥ 2) are degenerate with the upper sp-band of the metal [3]
Here, we report the results of an experimental
investigation of the image-potential states
and resonances on Ag(111) by means of timeresolved
2PPE and quantum-beat spectroscopy.
Although one might expect a rapid delocalization
of excited surface electrons into
the bulk in case of the resonances, the whole
series of states up to quantum numbers of
n = 7 could be observed. Even the time evolution
of prepared wave-packets could be probed,
just as for Cu(100) [2]. The measured binding
energies En are reproduced well by using
the same quantum defect a = 0.062 for the
Lifetime τ (fs)
1000
100
10
Ag(111)
experiment
theory
(n+0.062) 3
1 2 3 4 5 6 7
Quantum number n
(n = 1)-image-potential state in the sp-gap as well as for the resonances (n ≥ 2). The lifetimes
of the resonances (n ≥ 2) show good agreement with the n 3 -scaling law (Figure). Surprisingly,
the absolute values of the experimental lifetimes are even longer than theoretical ones. A
major difference between the Cu(100) image-potential states and the Ag(111) image-potential
resonances is a considerably shorter dephasing time of the latter.
[1] P. M. Echenique and J. B. Pendry, J. Phys. C 11, 2065 (1978)
[2] U. Höfer, I. L. Shumay, Ch. Reuß, U. Thomann, W. Wallauer, and Th. Fauster, Science 277, 1480
(1997)
[3] A. G. Borisov, E. V. Chulkov, and P. M. Echenique, Phys Rev. B 73, 073402 (2006)
73

Laser-induced photochemical reactions W11
Poster Wednesday 19:30
Hot Electron-induced Crystallization of Frozen Ammonia Film on Ag(111)
HYUKSANG KWON, SUNMIN RYU, KIWOOK HWANG, JUYEON PARK, and SEONG KEUN
KIM
Department of Chemistry, Seoul National University, Seoul, 151-747 Korea
vitalforce1@naver.com
The solvated electron (esol) and deep trapped electron (etrap) states for condensed ammonia were
probed by time- and angle-resolved 2-photon photoemission spectroscopy. The esol state with the
electron binding energy of ca. 1 eV was observed, in addition to the image-potential state (IPS),
at an NH3 coverage of 2 ML or lower on Ag(111), while the etrap state showed up at a higher
coverage with a trace of the esol state. The hot-electrons generated by the irradiation of a UV
light between 355 and 416 nm promote the evolution of the n = 1 IPS with a decrease in the etrap
state, which is viewed to be consistent with crystallization of the adsorbate layer. The observed
variation in the lifetime and effective mass of the photoexcited electron is also in accord with
such hot electron-induced phase transition.
74

W12 Laser-induced photochemical reactions
Poster Wednesday 19:30
Photochemistry of Excitonic States of C60 Surfaces
BENJAMIN GÖHLER, TIM HOGER, ARNE ROSENFELDT, and HELMUT ZACHARIAS
Universität Münster, Physikalisches Institut, 48149 Münster, Germany
hzach@uni-muenster.de
Time-delayed two-photon photoemission is employed to populate intermediate states in C60 and
probe their dynamics. The excitation probability of these states is measured as a function of photon
energy. The ordered C60 films with thicknesses between 10 and 200 ML are evaporated onto
Cu(111) and cooled down to 130 K. Using four-wave mixing in xenon radiation with a photon
energy of 8.27 eV (150 nm) is generated to observe occupied states and control the preparation.
Time-resolved measurements are performed using both a Q-switched laser with pulses of 3.5 eV
at 100 ns and a mode-locked laser tunable between 2.35 and 5.88 eV with about 75 ps pulse duration.
A rate equation fitted to the electron dynamics suggests a lifetime of about 126 ps for the
LUMO, 1 ns for the singlet exciton, and 23 µs for the triplet exciton. Lifetimes of the LUMO+1
and LUMO+2 are significantly shorter than 100 ps.
To observe the desorption of nitric oxide from fullerenes the surface is dosed with nitric oxide
and excited by a 3.5 eV ns laser pulse which is in resonance with the LUMO+1←HOMO and
the LUMO←HOMO−1 transition of the fullerene. Desorbing NO molecules are detected after
a defined flight distance with a probe laser ionizing the NO states specifically in a (1+1)-REMPI
process. The ionized molecules are accelerated in a reflectron time-of-flight mass spectrometer
and detected by micro channel plates. A bimodal arrival time distribution has been recorded with
a fast and a slow channel. The variation of the delay between desorption and probe laser yields for
a prompt desorption after a Jakobi transformation a velocity distribution. The fast channel yields
an averaged kinetic energy of 174 meV. Molecules arriving in the detection volume at times
as long as 500 µs after the desorption laser pulse in the slow channel correspond to a velocity
of 50 m/s, far too slow to be explained even by a thermal desorption. To further investigate these
seemingly slow molecules a field free drift tube has been built. The molecules drift through a
field free tube without further acceleration to detect their velocity. The fast channel yields a sharp
distribution of the velocity centered around the value expected for the respective desorption probe
delay. The slow channel yields a broad velocity distribution around 300 m/s independent of the
desorption probe delay. A broad velocity distribution, detected after a defined distance from the
surface and delay time with respect to the desorption laser pulse, can only be explained by a
delayed desorption. A half lifetime of the chemical active state of approximately τ ≈ 150 µs is
derived by combining different delays with the velocity distribution.
75

Spin-dependent dynamics and ultrafast magnetization W13
Poster Wednesday 19:30
Laser-Induced Magnetic Phase Transitions on FeRh Thin Films: a
Time-Resolved XMCD Study
ILIE RADU 1,2 , CHRISTIAN STAMM 2 , NIKO PONTIUS 2 , TORSTEN KACHEL 2 , P. RAMM 1 , J. U.
THIELE 3 , HERMANN A. DÜRR 2 , and C. H. BACK 1
1 Physics Department, University of Regensburg, Germany
2 BESSY GmbH, Berlin, Germany
3 Hitachi GST, San Jose Research Center, San Jose, USA
ilie.radu@physik.uni-regensburg.de
For close to equiatomic compositions the FeRh alloy undergoes a first-order magnetic phase transition
upon heating above room temperature. The transition from the antiferromagnetic (AFM) to
ferromagnetic (FM) state is accompanied by an isotropic lattice expansion of 1%. The AFM-FM
transition together with the relatively high magnetic moment of 4µB established in the FM phase,
make the FeRh alloy particularly interesting for heat-assisted magnetic recording [1].
In order to elucidate the elementary processes responsible for the laser-induced magnetization
growth and demagnetization of the FeRh alloy, we have employed time-resolved X-ray absorption
spectroscopy (XAS) and X-ray magnetic circular dichroism (XMCD) in a laser pump - X-ray
probe approach. The element specificity of these techniques allows us to disentangle and follow
the transient contribution of the Fe and Rh magnetic moments during the AFM-FM transition
and the transition towards the paramagnetic state. Upon fs laser excitation the build-up of the
ferromagnetic order develops with a characteristic time constant of ≈200 ps for both Fe and
Rh elements. This time scale is consistent with a magnetization growth mechanism [2] based
on the slow nucleation and expansion of the magnetic domains. Once in the FM state, FeRh
can be demagnetized on a sub-picosecond time scale as deduced by comparison to laser-induced
demagnetization dynamics of Ni [3] measured under similar conditions. Additional time-resolved
magneto-optics (MOKE) measurements performed with an improved time resolution of 200 fs,
corroborate the XMCD data showing a demagnetization behavior within ≈500 fs after photoexcitation.
We propose a demagnetization mechanism that follows the transient electronic temperature
of the system since the magnetization loss takes place while the excitation energy resides
in the electronic system.
[1] J. U. Thiele et al., Appl. Phys. Lett. 82, 2859 (2003)
[2] B. Bergmann et al., Phys. Rev. B. 73, 60407 (2006)
[3] C. Stamm et al., Nature Materials 6, 740 (2007)
76

W14 Spin-dependent dynamics and ultrafast magnetization
Poster Wednesday 19:30
Time-resolved and temperature dependent photoemission from a
ferromagnetic h-BN/Ni(111) surface
DOMINIK LEUENBERGER, MATTHIAS HENGSBERGER, and JÜRG OSTERWALDER
Physics Institute, University of Zürich, Switzerland
leuenber@physik.uzh.ch
Time-resolved photoemission (TR-PE) has been used to investigate ultrafast processes on solid
surfaces [1], for instance laser pulse induced hot carrier dynamics and demagnetization of
ferromagnetic materials on the femto-second time-scale [2,3]. Hexagonal boron nitride forms a
well-ordered monolayer on the Ni(111) surface. Many different techniques to study this interface
in detail have been applied by our group. Recent time-resolved two-photon photoemission
(2PPE) experiments gave evidence for the occurrence of surface states with rather high lifetimes
of the order of 100 fs [4]. Starting from previously investigated transitions on h-BN/Ni(111),
which are sensitive to the temperature dependent magnetic phase change in nickel, we introduce
an approach for studying ultrafast demagnetization processes and hot carrier dynamics by applying
TR-PE to h-BN/Ni(111). We will present time-resolved photoemission data as function of
temperature and time delay after absorption of an intensive laser pulse.
[1] A. B. Schmidt et al., Phys. Rev. Lett. 95, 107402 (2005)
[2] H. S. Rhie et al., Phys. Rev. Lett. 90, 247201 (2003)
[3] U. Bovensiepen, J. Phys.: Condens. Matter 19, 083201 (2007)
[4] M. Muntwiler et al., Phys. Rev. B 75, 075407 (2007)
77

Spin-dependent dynamics and ultrafast magnetization W15
Poster Wednesday 19:30
Spin calibration of an electron time-of-flight spin analyzer by spin-resolved
photoemission on Au(111) surface states
CÉPHISE M. CACHO 1,2 , MARCO MALVESTUTO 1 , SERGIO VLAIC 1 , ELAINE A. SEDDON 2 ,
and FULVIO PARMIGIANI 1
1 Sincrotrone Elettra, Trieste, Italy
2 STFC, Daresbury, England
cc53@dl.ac.uk
The spin-orbit coupling of the Au(111) surface states is measured by spin energy and angle
resolved photoemission at very low photon energy. High angle and energy resolution is achieved
by combining an electron Time-of-Flight spin analyzer with a 250 kHz fs laser source. Due to
the fact that both surface states are fully spin polarized, we show that the spin-resolved electron
distribution curves are self calibrated and the effective Sherman function of the Mott polarimeter
can be extracted. A study of the Mott polarimeter performances with the accelerating voltage
will be presented.
a) b)
Au(111)
sample
Time-of-Flight
Pulsed Photon
Source
Left
Detector
Right
Detector
Mott
Polarimeter
Intensity (a.u.)
6
5
4
3
2
1
0
0
Spin Up
Spin Down
200 400 600
Kinetic Energy (meV)
Fig. 1: a) Sketch of the experimental set up with the electron time-of-flight and the Mott polarimeter
for the spin resolution. The Au(111) surface is excited by a 200 nm (6.2 eV) laser beam. b)
Spin-integrated (black curve) and spin-resolved electron distribution curve measured at 12 ◦ from
normal emission by direct photoemission. Both spin up and spin down surface states are clearly
resolved just below the Fermi edge.
78
800

W16 Advances in ultrafast surface spectroscopies
Poster Wednesday 19:30
Core-level shifts induced by femtosecond laser excitation
ANDREA MELZER, DANIEL KAMPA, JINXIONG WANG, and THOMAS FAUSTER
Lehrstuhl für Festkörperphysik, Universität Erlangen, Germany
Thomas.Fauster@physik.uni-erlangen.de
The Si(001)(2x2)-Ga surface was used to investigate time-dependent Ga(3d) core-level shifts by
pumping electrons from the valence to the conduction band by femtosecond laser pulses with
1.59 eV photon energy. The Ga(3d) core level was probed with higher harmonics generated in
argon from the same laser source (multipass amplifier, 1.4 mJ pulse energy, 30 fs pulse duration,
779 nm wavelength, 1 kHz repetition rate). The time resolution for the 25th harmonic (40 eV
photon energy) was ∼ 400 fs after a grating monochromator.
The band bending of about 110 meV of the p-doped Si(001)(2x2)-Ga surface is completely lifted
by illumination of the surface with 1.59 eV laser pulses. The Ga(3d) core level shows a slow timedependent
shift attributed to the build-up (∼ 1 ns) and decay (∼ 100 ns) of the photovoltage.
Pumping electrons from valence to conduction states should change the screening of the core
hole. The lifetimes of these excitations are expected to be considerably smaller than the time
scales of the photovoltage changes. On the subpicosecond timescale upper limits for the Ga(3d)
core-level shift and broadening were determined to be less than 20 meV at the used pump pulse
intensity of 20 mJ/cm 2 . Experiments with pump pulses of 3.18 eV photon energy showed similar
results. Possible reasons for the small core-level shift will be discussed.
79

Advances in ultrafast surface spectroscopies W17
Poster Wednesday 19:30
A femtosecond X-ray/optical cross-correlator: Free-electron laser X-ray
pulse induced transient optical reflectivity
CORNELIUS GAHL 1,4 , ARMIN AZIMA 3 , MARTIN BEYE 2 , MARTIN DEPPE 2 ,
KRISTIAN DÖBRICH 1,4 , URS HASSLINGER 2 , FRANZ HENNIES 2,5 , ALEXEY MELNIKOV 1 ,
MITSURU NAGASONO 2 , ANNETTE PIETZSCH 2 , MARTIN WOLF 1 , WILFRIED WURTH 2 , and
ALEXANDER FÖHLISCH 2
1 Freie Universität Berlin, Germany
2 Universität Hamburg, Germany
3 HASYLAB/DESY, Hamburg, Germany
4 Max-Born-Institut Berlin, Germany
5 MAX-lab, Lund Universitet, Sweden
doebrich@mbi-berlin.de
Free-electron-laser (FEL) based femtosecond (fs) X-ray pulse sources make new classes of experiments
feasible, due to their short pulse duration and high brilliance over a wide range of photon
energies. For pump-probe measurements, it is a key issue to precisely synchronize the FEL with
an external fs laser source. To this end, one has to determine the relative arrival time of X-ray
and optical pulses to perform pump-probe experiments with time resolution on the fs scale. We
exploited the high peak brilliance available at the FEL in Hamburg (FLASH) for measuring the
X-ray induced transient change in optical reflectivity at a GaAs surface [1]. The observed ultrafast
drop in reflectivity on the time scale of the pulse durations renders it possible to determine
the temporal overlap between X-ray and optical pulses as well as the statistical timing jitter and
systematical temporal drifts within a pulse train. This technique is easy to set up parallel to other
user experiments and therefore is suitable as a diagnosis tool. Thus, the use of GaAs as medium
for a fs X-ray/optical cross-correlator represents an important step towards delay control for fs
time-resolved experiments and opens the field of fs X-ray-induced and -probed dynamics.
[1] C. Gahl et al., Nature Photonics 2, 165 (2008)
80

Correlated materials
9:00 VO2 as a Model System for Electron-Phonon Dynamics in Correlated Materials
Alfred Leitenstorfer, Carl Kübler, Rupert Huber
9:40 Energy dissipation at surfaces and the Jarzynski relation
Kurt Schönhammer
10:20 Coffee break
Thursday morning
11:00 Collective excitations of charge density compound TbTe3 analysed by time- and angleresolved
photoemission spectroscopy
Patrick S. Kirchmann, F. Schmitt, U. Bovensiepen, R. G. Moore, L. Rettig, M. Krenz,
J.-H. Chu, N. Ru, L. Perfetti, D. Lu, M. Wolf, I. Fisher, Z.-X. Shen
11:20 Time Resolved Photoemission and Time Resolved THz on High Temperature Supercondutors
Luca Perfetti, Panagiotis Loukakos, Uwe Bovensiepen, Martin Scheuch, Tobias
Kampfrath, Martin Wolf
12:00 Nonadiabatic dynamics of electron scattering from adsorbates in surface bands
Branko Gumhalter, Antonio ˇSiber, Hrvoje Buljan
12:20 Laser and Low-Energy ARPES of High-Tc Superconductors
Dan Dessau
13:00 Break
13:20 Lunch
81

Wave-packet dynamics
Invited talk Thursday 9:00
VO2 as a Model System for Electron-Phonon Dynamics in Correlated
Materials
ALFRED LEITENSTORFER, CARL KÜBLER, and RUPERT HUBER
Department of Physics and Center for Applied Photonics, University of Konstanz, Germany
aleitens@uni-konstanz.de
The insulator-metal transition in VO2 represents a prototype phenomenon typical for strongly
correlated electron systems [1]. When cooling the compound below a critical temperature of TL
= 340 K, the high-temperature metallic phase transforms into a dielectric while dimerization of
V atoms reduces the crystal symmetry from rutile to monoclinic. Surprisingly, this first-order
transition may be switched on a femtosecond time scale via ultrafast photoexcitation of electronhole
pairs over the dielectric bandgap of 0.7 eV.
We investigate the microscopic origin of this process with a resolution of 10 fs [2]. The complex
infrared conductivity is sampled via field-resolved spectroscopy with multi-THz transients [3].
The data include the spectral signatures of electronic and ionic degrees of freedom, precisely
unraveling their interplay. Our findings motivate a qualitative picture for the ultrafast dynamics
of the insulator-metal transition. The model is inspired by recent cluster dynamical mean-field
theory treating the strong electronic correlations in the dielectric phase on a two-electron Heitler-
London basis for the V-V dimers [4]. In the earliest stage, the dynamics initiated by the femtosecond
pulse resembles the local excitation of the dimers into an antibonding state, triggering
a coherent wave packet of a V-V stretching mode at 6 THz. At moderate excitation fluence,
the strong correlations between the two binding electrons of each dimer are re-established on a
subpicosecond time scale and the mid-IR electronic conductivity vanishes rapidly. However, if
the density of excited lattice sites exceeds a threshold value, coherent phonon oscillations and
thermal fluctuations drive the system to a point where electronic correlations can no longer be
restored and the metallic phase is stabilized. The high speed of the phase transition is explained
by the fact that the wave packet motion in the excited state elegantly pushes the monoclinic lattice
towards rutile symmetry. Interestingly, the electronic conductivity settles to a constant value
already after one V-V oscillation cycle while the lattice oscillates coherently for approximately
1 ps. This behavior beyond the Born-Oppenheimer approximation is a clear fingerprint of the
strongly correlated character of the electronic system underlying these phenomena.
[1] F. J. Morin, Phys. Rev. Lett. 3, 34 (1959)
[2] C. Kübler et al., Phys. Rev. Lett. 99, 116401 (2007)
[3] R. Huber et al., Appl. Phys. Lett. 76, 3191 (2000); C. Kübler et al., ibid. 85, 3360 (2004)
[4] S. Biermann et al., Phys. Rev. Lett. 94, 026404 (2005)
82

Electronic energy transfer
Invited talk Thursday 9:40
Energy dissipation at surfaces and the Jarzynski relation
KURT SCHÖNHAMMER
Institut für Theoretische Physik, Universität Göttingen, Germany
schoenh@theorie.physik.uni-goettingen.de
Inelastic scattering of atoms from surfaces has attracted large interest, both experimentally and
theoretically. At metal surfaces the low energy loss occurs through the excitations of phonons
and electron-hole pairs. While the case of weak inelasticity is theoretically well understood the
description of strong inelasticity is often simplified assuming that the adsorbate motion can be
treated classically. Only for simplified models the complete probability distribution P (ɛ) of the
energy loss was calculated exactly.
Very few exact theoretical results are known in the field of nonequilibrium statistical mechanics.
In connection with fluctuations in small systems Jarzynski [1] derived an exact identity which
relates nonequilibrium measurements of work done on a system to equilibrium free energy differences[2].
Adapted to the problem addressed above the Jarzynski relation (JR) yields a new sum
rule for P (ɛ) . Earlier theoretical results are examined in the light of this development. For some
simple models the JR turns out to be just a detailed balance relation valid for arbitrary strength
of the inelasticity.
[1] J. Jarzynski, Phys. Rev. Lett. 78, 2690 (1997)
[2] C. Bustamante, J. Liphardt, and F. Ritort, Physics Today, July 2005, 43
83

Coherent phenomena
Talk Thursday 11:00
Collective excitations of charge density compound TbTe3 analysed by timeand
angle-resolved photoemission spectroscopy
PATRICK S. KIRCHMANN 1 , F. SCHMITT 2 , UWE BOVENSIEPEN 1 , R. G. MOORE 2,3 , LAURENZ
RETTIG 1 , MARCEL KRENZ 1 , J.-H. CHU 2 , N. RU 2 , LUCA PERFETTI 1 , D. LU 3 , MARTIN
WOLF 1 , I. FISHER 2,4 , and Z.-X. SHEN 2,3
1 Fachbereich Physik, Freie Universität Berlin, Germany
2 Department of Applied Physics, Stanford University, CA 94305, USA
3 Stanford Synchrotron Radiation Laboratory, Stanford University, CA 94305, USA
4 Geballe Laboratory for Advanced Materials, Stanford University, CA 94305, USA
patrick.kirchmann@physik.fu-berlin.de
The formation of a charge density wave (CDW) due to Fermi surface (FS) nesting are one of
the promising examples for the study of collective modes and excitations in many-body quantum
systems [1]. Recent advances in femtosecond time- and angle-resolved photoemission spectroscopy
(trARPES) allow the simultaneous analysis with respect to the single-particle information
in the frequency- and the collective information in the time-domain [2].
We have performed trARPES on the CDW compound TbTe3 using 1.5 eV pump pulses and
6.0 eV probe pulses with 90 fs pulse duration. We observe two optically excited collective modes
which differ qualitatively. The first mode induces binding energy oscillations of a Te-derived
band, which are momentum-independent at all investigated pump fluences and temperatures and
thus is assigned to a generic Te derived phonon. The second mode is identified as the amplitude
mode of the TbTe3 CDW system due to the following arguments (i) it modulates the spectral
function of the CDW state, it is observed only well (ii) in the charge ordered phase exclusively
in the nesting region of the FS, (iii) for sufficiently low temperatures, and (iv) for low enough
fluence (F = 0.3 mJ/cm 2 ) to remain in a weakly-perturbative excitation regime. An increase
of pump fluence to F = 2 mJ/cm 2 drives the CDW into a perturbative regime which is characterized
by an ultrafast melting of the charge-ordered state within ∼ 100 fs. This disintegration
of the CDW phase is evidenced by a transient closing of the CDW gap and transient recurrence
of a quasi-free electron like dispersion of the CDW band. The unprecedented insight into the
intriguing correlation of the electronic spectral function and collective modes on the real time
electronic structure establishes trARPES as an effective tool for the study of prevailing questions
in many-particle physics and correlated electron systems.
[1] V. Brouet et al., Phys. Rev. Lett. 93, 126405 (2004); N. Ru et al., Phys. Rev. Lett. 77, 035114
(2008)
[2] L. Perfetti et al., Phys. Rev. Lett. 97, 067402 (2006); P. A. Loukakos et al., Phys. Rev. Lett.
98, 097401 (2007)
84

Electronic energy transfer
Invited talk Thursday 11:20
Time Resolved Photoemission and Time Resolved THz on High
Temperature Supercondutors
LUCA PERFETTI, PANAGIOTIS LOUKAKOS, UWE BOVENSIEPEN, MARTIN SCHEUCH,
TOBIAS KAMPFRATH, and MARTIN WOLF
Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
perfetti@physik.fu-berlin.de
Time resolved photoelectron spectroscopy and Time Resolved THz are employed to study the dynamics
of photoexcited electrons in optimally doped Bi2Sr2CaCu2O8+δ (Bi-2212). Hot electrons
thermalize in less than 50 fs and dissipate their energy on two distinct timescales (110 fs and 2
ps). These are attributed to the generation and subsequent decay of non-equilibrium phonons, respectively.
We conclude that 20% of the total lattice modes dominate the coupling strength. The
average electron-phonon coupling of the copper-oxygen bonds is surprisingly weak. Moreover,
Time resolved THz measurements indicate that the Drude scattering rate depends only on the
electronic temperature. Finally, we present a novel and accurate method to extract the specific
heat of the electronic subsystem.
(a) (b)
e
(c)
Delay
6 eV 1.5 eV
M Y
k F
Γ M
Low High
-1.0 0
k-k F (nm -1 )
[1] L. Perfetti, P. A. Loukakos, M. Lisowski, U. Bovensiepen, H. Eisaki, and M. Wolf, Phys. Rev.
Lett. 99, 197001 (2007)
85
-0.1
0.0
0.1
0.2
0.3
Binding Energy (eV)

Wave-packet dynamics
Talk Thursday 12:00
Nonadiabatic dynamics of electron scattering from adsorbates in surface
bands
BRANKO GUMHALTER 1 , ANTONIO ˇSIBER 1 , and HRVOJE BULJAN 2
1 Institute of Physics, Zagreb, Croatia
2 Faculty of Science, Zagreb, Croatia
branko@ifs.hr
We present a comparative study of nonadiabatic dynamics of intra-band electron scattering in
quasi-two-dimensional surface bands which is induced by the long-range component of the interactions
with a random array of adsorbates[1]. Using three complementary model descriptions
of spatio-temporal propagation of quasiparticles that go beyond the single adsorbate scattering
approach we are able to identify distinct subsequent regimes of evolution of an electron following
its promotion into an unoccupied band: (i) early quadratic decay of the initial state survival probability
within the Heisenberg uncertainty window, (ii) preasymptotic exponential decay governed
by the self-consistent Fermi golden rule scattering rate, and (iii) asymptotic decay described by
a combined inverse power-law and logarithmic behavior. The developed models are applied to
discuss the dynamics of intra-band adsorbate-induced scattering of hot electrons excited into the
n=1 image potential band on Cu(100) surface during the first stage of a two-photon photoemission
process. This situation is illustrated in the figure below which shows the scattered electron
wavelengths λ = 2π/K for the initial momenta K = 0.0836 a.u. and K = 0.1672 a.u. in comparison
with spatially random distribution of adsorbates at the coverage of 0.7 % [1]. Estimates of
crossovers between the distinct evolution regimes enable the assessment of the range of applicability
of the widely used Fermi golden rule and optical Bloch equations approach for description
of adsorbate-induced quasiparticle decay and dephasing in ultrafast experiments.
[1] K. Boger, Th. Fauster, and M. Weinelt, New J. Phys. 7, 110 (2005)
86

Advances in ultrafast surface spectroscopies
Invited talk Thursday 12:20
Laser and Low-Energy ARPES of High-Tc Superconductors
DAN DESSAU
Dept. of Physics, University of Colorado, Boulder, Colorado, USA
dessau@colorado.edu
We have developed a system to do high-resolution angle-resolved photoemission using laser
sources. Compared to conventional ARPES we obtain greatly improved energy resolution, momentum
resolution, bulk sensitivity, plus reduced final-state broadening effects. We have used
this to study the electronic structure and quasiparticle dynamics of high-temperature superconductors.
For the first time, spectral widths/lifetimes are consistent with expectations from other
spectroscopies (e. g. optics), confirming the intrinsic or near-intrinsic spectral lineshapes. I will
discuss some of our recent results using this spectroscopy, including potential extensions such as
pump-probe laser-ARPES.
[1] J. D. Koralek et al., Phys. Rev. Lett. 96, 017005 (2006)
[2] J. D. Koralek et al., Rev. Sci. Instrum. 78, 053905 (2007)
[3] Philip A. Casey et al., Nature Physics 4, 210 (2008)
87

Thursday afternoon
Ultrafast microscopy and coherent control
14:40 Femtosecond Electron Diffraction: Atomic Perspective of Condensed Phase Dynamics
R. J. Dwayne Miller
15:20 Ultra-fast time resolved electron diffraction at surfaces: Electron-phonon coupling, heat
transfer and discrete phonons in Bi(111)-heterofilms on Silicon
Anja Hanisch, B. Krenzer, S. Möllenbeck, T. Pelka, P. Schneider, M. Horn-von Hoegen
15:40 Adaptive nanooptics
Walter Pfeiffer
16:20 Time Resolved and Non-Linear Photoemission Electron Microscopy on Self-assembled
and Polycrystalline Ag-Nanoparticles
Niemma M. Buckanie, L. I. Chelaru, N. Raß S. Möllenbeck, F.-J. Meyer zu Heringdorf
16:40 Coffee break
17:20 Unoccupied electronic states at the lead phthalocyanine (PbPc)/graphite interface measured
with two-photon photoemission microspectroscopy
M. Shibuta, R. Yamamoto, T. Yamada, K. Miyakubo, Toshiaki Munakata
17:40 Toward Coherent Control in the Nanoscale
Tamar Seideman, Maxim Sukharev
18:20 Ultrafast surface plasmonics: Imaging light with electrons on the femto/nano scale
Hrvoje Petek, A. Kubo
19:00 Break
19:30 Conference Dinner
88

Laser-induced photochemical reactions
Invited talk Thursday 14:40
Femtosecond Electron Diffraction: Atomic Perspective of Condensed Phase
Dynamics
R. J. DWAYNE MILLER
Departments of Chemistry and Physics, Institute for Optical Sciences, University of Toronto,
Canada
dmiller@lphys.chem.utoronto.ca
Femtosecond Electron Diffraction harbours great potential for providing atomic resolution to
structural changes as they occur, essentially watching atoms move in real time and directly observe
transition states. This experiment has been referred to as “making the molecular movie” and
has been previously discussed in the context of a classic gedanken experiment, outside the realm
of direct observation. With the recent development of femtosecond electron pulses with sufficient
number density to execute nearly single shot structure determinations, this experiment has been
finally realized. A new concept in electron pulse generation was developed based on a solution
to the N-body electron propagation problem involving up to 10,000 interacting electrons that
has led to a new generation of extremely “bright” electron pulsed sources that minimizes space
charge broadening effects. Previously thought intractable problems of determining t = 0 and
fully characterizing electron pulses on the femtosecond time scale have now been solved through
the use of the laser pondermotive potential to provide a time dependent scattering source. Synchronization
of electron probe and laser excitation pulses is now possible with an accuracy of
10 femtoseconds to follow even the fastest nuclear motions. The camera for the “molecular movie”
is now in hand. Atomic level views of the simplest possible structural transition, melting,
have been obtained for a number of metals under strongly driven conditions (up to warm dense
matter conditions) under which the dynamics occur over nm or molecular lengths scales. Direct
observation of phonon distortions involved in electron-scattering and electronically driven structure
changes in Si can now be resolved. Applications to specific molecular systems will also be
discussed in the context of directly imaging reaction dynamics at the atomic level of inspection.
89

Wave-packet dynamics
Talk Thursday 15:20
Ultra-fast time resolved electron diffraction at surfaces: Electron-phonon
coupling, heat transfer and discrete phonons in Bi(111)-heterofilms on
Silicon
ANJA HANISCH, B. KRENZER, S. MÖLLENBECK, T. PELKA, P. SCHNEIDER, and M.
HORN-VON HOEGEN
Department of Physics, Universität Duisburg-Essen, D-47057 Duisburg, Germany
anja.hanisch@uni-due.de
In an ultra-fast time resolved reflection high energy electron diffraction (TR-RHEED) setup we
studied the transient temperature of ultra-thin epitaxial Bi(111) films on Silicon upon fs-laser
excitation. As the diffraction patterns are directly related to the surface structure, the transient
structure can be determined in a pump-probe setup by changing the delay between optical pump
an electron probe pulse. In addition, using the Debye-Waller Effect the evolution of the diffraction
spot intensity can be converted to a transient surface temperature [1].
The initial temperature increase is determined by electron-phonon coupling, which leads to the
heating of the phonon system of the Bi film in 20 ps. Then the temperature drops slowly with an
exponential decay of 640 ps for a 6 nm Bi film [1]. This slow cooling rate is determined by the
thermal boundary resistance at the interface between Bi and Si which is strongly enhanced by the
total internal reflection of the phonons at the Bi/Si interface: the heat is trapped in the Bi-film!
With increasing Bi film thickness a linear increase of the decay constant τ from 240 ps up to
3300 ps is observed for 2.5 nm to 35 nm thick Bi films on Si(111). For Bi on Si(001) the same
linear relationship between τ and the film thickness is observed for films thicker than 6 nm
[2] while for thinner films the cooling rate τ becomes independent of the film thickness, i.e.
the thermal boundary resistance has strongly increased which cannot be explained in terms of
existing models. An interesting difference between the two heterosystems is the formation of an
interfacial dislocation network accommodating the lattice mismatch between Bi(111) on Si(001).
The film is relaxed, which is not the case for Bi on Si(111) [3]. Additionally we expect for the
thinnest film of only 2.8 nm thickness a discrete phonon spectrum normal to the interface with
only a few vibrational modes which obviously increases the thermal boundary resistance.
[1] B. Krenzer et al., New J. Phys. 8, 190 (2006)
[2] A. Hanisch et al., Phys. Rev. B 77, 125410 (2008)
[3] G. Jnawali et al., Phys. Rev. B 74, 195340 (2006)
90

Coherent phenomena
Invited talk Thursday 15:40
Adaptive nanooptics
WALTER PFEIFFER
Fakultät für Physik, University of Bielefeld, Germany
pfeiffer@physik.uni-bielefeld.de
The precise spatial, temporal, and vectorial properties of the electromagnetic near-field are of
vital importance, and hence specific control over nanooptical field properties is of great interest.
The excitation of nanostructures with broadband coherent radiation provides flexible means
to control the electromagnetic field. In particular the combination of polarization shaping and
evolutionary optimization allows controlling the spatial and temporal evolution of nanoscopic
near-field distributions [1]. Different theoretical examples demonstrating the flexibility and broad
applicability of this control scheme are presented and the underlying mechanisms for field control
are discussed. Besides spatial and temporal properties the local control of the spectral density
might be of significant interest [2].
To demonstrate this scheme experimentally we have performed two-photon photoemission electron
microscopy using a planar nanostructure in combination with adaptive polarization pulse
shaping [3]. The photoemission pattern reflects the local optical near-field and depends critically
on the polarization state of the incident laser pulse. The experiments and the comparison with
theory demonstrate that electric near-fields and photoemission patterns can indeed be controlled
on a sub-diffraction (tens of nanometers) length scale, Time-resolved 2-PEEM cross correlation
measurements allow monitoring the local field evolution and show that the emission from different
regions of the nanostructure exhibit a controlled variation of their relative intensities within
time scales limited only by the spectral bandwidth of the used coherent light source.
[1] T. Brixner, F. J. García de Abajo, J. Schneider, and W. Pfeiffer, Nanoscopic ultrafast spacetime-resolved
spectroscopy, Phys. Rev. Lett. 95, 093901 (2005)
[2] T. Brixner, F. J. García de Abajo, J. Schneider, C. Spindler, and W. Pfeiffer, Ultrafast adaptive
optical near-field control, Phys. Rev. B 73, 125437 (2006)
[3] M. Aeschlimann, M. Bauer, D. Bayer, T. Brixner, F. J. García de Abajo, W. Pfeiffer, M.
Rohmer, C. Spindler, and F. Steeb, Adaptive subwavelength control of nano-optical fields, Nature
446, 301 (2007)
91

Wave-packet dynamics
Talk Thursday 16:20
Time Resolved and Non-Linear Photoemission Electron Microscopy on
Self-assembled and Polycrystalline Ag-Nanoparticles
NIEMMA M. BUCKANIE, L. I. CHELARU, N. RASS, S. MÖLLENBECK, and F.-J. MEYER ZU
HERINGDORF
Department of Physics, Universität Duisburg-Essen, D-47057 Duisburg, Germany
niemma.buckanie@uni-due.de
The combination of non-linear photoemission electron microscopy (PEEM) with ultrashort laser
pulses for illumination allows to study the collective electronic excitations in metals (plasmons)
in the space and time domain. Two photon photoemission experiments (2PPE) give us an insight
into the dynamic of the surface plasmons and provide information about the propagation and
decay of plasmons. In our 2PPE experiments, a first photon of the energy E = 3.1 eV excites
a plasmon in Ag-nanostructures. The absorption of a second photon by the plasmon generates
photoelectrons that are used for imaging in PEEM. By variation of the delay between the two
involved photons, time resolved (TR) experiments can be performed. For such TR-PEEM experiments
an actively stabilized Mach-Zehnder interferometer provides time shifted pump and
probe pulses with an accuracy in the as regime. The possibility of in-situ preparation of Ag single
crystalline structures with high quality provides for an excellent experimental system. Since the
self assembling capabilities of the single crystalline structures do not offer particles of all desired
shapes and orientations, we accompany our studies with particles that were created by e-beam
lithography.
92

Electronic energy transfer
Talk Thursday 17:20
Unoccupied electronic states at the lead phthalocyanine (PbPc)/graphite
interface measured with two-photon photoemission microspectroscopy
M. SHIBUTA, R. YAMAMOTO, T. YAMADA, K. MIYAKUBO, and TOSHIAKI MUNAKATA
Department of Chemistry, Graduate School of Science, Osaka University, Toyonaka, Osaka
560-0043 Japan
munakata@ch.wani.osaka-u.ac.jp
We have measured unoccupied electronic states of lead phthalocyanine (PbPc) films of 1 monolayer
thickness formed on graphite substrates (HOPG). Highly-reproducible and well-resolved
2PPE spectra were obtained by selecting uniform sample areas with sub-micrometer light spot.
Figure 1 shows 2PPE spectra measured with different photon energies (Phys. Rev. B77, 115404
(2008)). All the spectral features were very sharp, typically narrower than 0.3 eV. We have identified
the molecule-derived states due to HOMO-1, HOMO, LUMO, LUMO+1, LUMO+2 as well
as the first image-potential state (IS). The energy levels are shown in Fig.2. Resonant excitation
between the HOMO and LUMO+2-related levels as well as that between the HOMO-related
level and IS were observed in consistency with energies of relevant levels determined from offresonant
conditions. The resonances indicate that the unoccupied states are populated by optical
transitions and not by photon-induced electron transfer from the substrate. We will discuss the
lifetimes of electrons in the unoccupied states. When the image of the film was measured with
the intensity of the occupied states features, the film became uniform by a suitable annealing
process. But when the images were measured with the unoccupied features, the surface was still
inhomogeneous. The difference of the images suggests the contribution of T2 on the intensity of
the unoccupied features.
93

Coherent phenomena
Invited talk Thursday 17:40
Toward Coherent Control in the Nanoscale
TAMAR SEIDEMAN and MAXIM SUKHAREV
Northwestern University, Evanston, USA
t-seideman@northwestern.edu
Inelastic electron tunneling via molecular-scale junctions can induce a variety of fascinating dynamical
processes in the molecular moiety. These include vibration, rotation, inter-mode energy
flow and reaction. Potential applications of current-driven dynamics in heterojunctions range
from new forms of molecular machines and new modes of conduction, to new directions in surface
nanochemistry and nanolithography.
In the first part of the talk, I will discuss the qualitative physics underlying current-driven dynamics
in molecular-scale devices, outline the theory we developed to explore these dynamics,
describe the results of ongoing research on surface nanochemistry and molecular machines, and
sketch several of our dreams and plans in these areas (for a review, see [1]).
The application of light to control molecular motions and electronic transport in junctions is intriguing,
since photonic (by contrast to electronic) sources offer (sub)femtosecond time resolution
and tunable phase and polarization properties. It is, however, challenging, since it requires intense
light sources that are tightly localized in space. It is here that plasmonics offer an opportunity.
In the second part of the talk, we will combine
plasmonics physics with concepts and tools
borrowed from coherent control of molecular
dynamics with two goals in mind. One is to
introduce new function into nanoplasmonics,
including ultrafast elements and broken symmetry
elements. The second is to develop coherent
nanoscale sources and apply them to
coherent control of both molecular dynamics
and electric transport in the nanoscale (for a review,
see [2]). Several simple elements in what
we envision developing into coherently controlled
nanoplasmonics are schematically illustrated
in Fig. 1. To conclude the talk, we will
return to nanoelectronics, and illustrate the application
of plasmonics to current control, with
a view to ultrafast electric switches.
[1] T. Seideman, J. Phys: Condens. Matter 15, R521 (2003)
[2] M. Sukharev and T. Seideman, J. Phys. B 40, S283 (2007)
94

Laser-induced photochemical reactions
Invited talk Thursday 18:20
Ultrafast surface plasmonics: Imaging light with electrons on the
femto/nano scale
HRVOJE PETEK 1,2 and A. KUBO 1,3,4
1 Department of Physics and Astronomy, University of Pittsburgh, USA
2 Donostia International Physics Center, San Sebastian, Spain
3 Department of Physics, University of Tsukuba, Japan
4 Japan Science and Technology Agency
petek@pitt.edu
Light interacting with a metal surface can excite both single-particle (e-h pair) and collective
(plasmon) excitations. While most of the incident field will be coherently reflected, a small fraction
can be absorbed to excite electron-hole pairs within the skin depth of the metal, or localized
and propagating plasmon modes. We investigate electron excitation at clean, single crystal metal
surfaces by ultrafast nonlinear momentum and energy, resolved photoemission spectroscopy
and photoemission electron microscopy. We discuss the imaging of surface plasmon polariton
dynamics on Ag surfaces and the function of simple plasmonic optical elements [1-3].
[1] A. Kubo et al., Nano Lett. 5, 1123 (2005)
[2] A. Kubo, N. Pontius, and H. Petek, Nano Lett. 7, 470 (2007)
[3] A. Kubo, Y. S. Jung, H. K. Kim, and H. Petek, J. Phys. B 40, S259 (2007)
95

Author Index
Abel, Bernd
Wednesday 11:00, 49
Aeschlimann, Martin
Monday 19:30, 38
Tuesday 9:40, 41
Wednesday 12:00, 51
Wednesday 12:20, 52
Wednesday 12:40, 53
Anderson, Alexandria
Wednesday 17:20, 60
Andreyev, Oleksiy
Wednesday 19:30, 66
Apolonskiy, A.
Monday 19:30, 100
Arafune, Ryuichi
Monday 18:00, 19
Arnolds, Heike
Monday 19:30, 28
Arrell, Christopher
Monday 19:30, 36
Aydil, Eray S.
Wednesday 19:30, 68
Azima, Armin
Wednesday 19:30, 80
Back, C. H.
Wednesday 19:30, 76
Bauer, Michael
Monday 19:30, 38
Wednesday 12:00, 51
Wednesday 12:20, 52
Wednesday 12:40, 53
Wednesday 19:30, 66
Bayer, Daniela
Monday 19:30, 38
Bdˇzoch, Juraj
Wednesday 15:20, 56
Beye, Martin
Wednesday 19:30, 80
Beyer, Markus
Monday 19:30, 25
Biedermann, Kerstin
Monday 19:30, 22
Biljakovic, Katica
Monday 19:30, 25
Bisio, Francesco
Monday 18:30, 20
Wednesday 19:30, 70, 72
Bonn, Mischa
Wednesday 18:20, 62
Borisov, Andrei G.
Monday 11:20, 11
Wednesday 19:30, 65
Bovensiepen, Uwe
Donath, Markus
Monday 19:30, 23, 26, 34, 37 Monday 19:30, 33
Tuesday 11:00, 42
Tuesday 11:50, 44
Tuesday 11:20, 43 Dürr, Hermann A.
Wednesday 19:30, 64
Monday 19:30, 34
Thursday 11:00, 84
Tuesday 11:00, 42
Thursday 11:20, 85
Tuesday 11:20, 43
Bredenbeck, Jens
Wednesday 19:30, 76
Wednesday 18:20, 62 Düsterer, Stefan
Brixner, Tobias
Wednesday 15:40, 57
Monday 19:30, 38 Duncker, Klaus
Buckanie, Niemma M.
Wednesday 19:30, 69
Thursday 16:20, 92 Eberhardt, Wolfgang
Bulgakova, N.
Monday 19:30, 34
Tuesday 11:20, 43
Tuesday 11:00, 42
Buljan, Hrvoje
Tuesday 11:20, 43
Thursday 12:00, 86 Echenique, Pedro M.
Cacho, Céphise M.
Monday 9:00, 8
Wednesday 19:30, 78 Eickhoff, Christian
Campen, R. Kramer
Monday 19:30, 35
Wednesday 18:20, 62 Faubel, M.
Carley, Robert
Wednesday 11:00, 49
Monday 19:30, 27, 35 Fauster, Thomas
Catton, Emma
Monday 19:30, 22
Monday 19:30, 36
Wednesday 19:30, 79
Chelaru, L. I.
Fernandez, A.
Thursday 16:20, 92
Monday 19:30, 100
Chiang, Cheng-Tien
Fischer, Alexander
Wednesday 19:30, 70, 72 Monday 19:30, 38
Chu, J.-H.
Wednesday 12:40, 53
Thursday 11:00, 84 Fisher, I.
Constantinescu, Anca-Monia Thursday 11:00, 84
Wednesday 17:50, 61 Föhlisch, Alexander
Cunovic, Stefan
Wednesday 19:30, 80
Monday 19:30, 38 Freund, Hans-Joachim
Damm, Andreas
Monday 19:30, 32
Wednesday 19:30, 67 Freyer, Wolfgang
Deicke, Frederik
Monday 19:30, 27
Wednesday 12:00, 51 Frigge, Robert
Demsar, Jure
Wednesday 15:40, 57
Monday 19:30, 25 Frischkorn, Christian
Deppe, Martin
Wednesday 15:20, 56
Wednesday 19:30, 80 Fürbach, A.
Dessau, Dan
Monday 19:30, 100
Thursday 12:20, 87 Fuji, T.
Díaz-Tendero, Sergio
Monday 19:30, 100
Monday 11:20, 11 Gahl, Cornelius
Wednesday 19:30, 65
Monday 19:30, 27, 34, 35
Dimler, Frank
Tuesday 11:00, 42
Monday 19:30, 38
Tuesday 11:20, 43
Döbrich, Kristian
Wednesday 19:30, 80
Wednesday 19:30, 80 Gauyacq, Jean-Pierre
96

Monday 11:20, 11
Wednesday 12:40, 53
Wednesday 19:30, 65
Ghosh, Avishek
Wednesday 18:20, 62
Giese, Philipp
Wednesday 15:20, 56
Giesen, Fabian
Monday 19:30, 33
Gießel, Tanja
Tuesday 11:20, 43
Göhler, Benjamin
Wednesday 19:30, 75
Goris, Andreas
Monday 19:30, 33
Grubmüller, H.
Wednesday 11:00, 49
Güdde, Jens
Monday 19:30, 30
Wednesday 19:30, 67
Gumhalter, Branko
Thursday 12:00, 86
Hada, Masaki
Wednesday 19:30, 71
Hanisch, A.
Monday 19:30, 31
Hanisch, Anja
Thursday 15:20, 90
Harris, Charles B.
Monday 9:40, 9
Hase, Muneaki
Monday 19:30, 29
Wednesday 16:20, 59
Wednesday 17:50, 61
Hasslinger, Urs
Wednesday 19:30, 80
Heinz, Tony F.
Sunday 18:20, 6
Hellsing, Bo
Monday 11:00, 10
Hengsberger, Matthias
Wednesday 19:30, 77
Hennies, Franz
Wednesday 19:30, 80
Hertel, Tobias
Monday 17:20, 18
Himpsel, Franz J.
Monday 19:30, 22
Höfer, Ulrich
Monday 12:00, 12
Monday 19:30, 30
Wednesday 19:30, 67, 73
Hoger, Tim
Wednesday 15:40, 57
Wednesday 19:30, 75
Horn-von Hoegen, M.
Monday 19:30, 31
Thursday 15:20, 90
Huber, Rupert
Thursday 9:00, 82
Huchon, Christophe
Monday 19:30, 36
Husser, Henning
Monday 14:40, 15
Hwang, Kiwook
Wednesday 19:30, 74
Ichibayashi, Taku
Monday 12:40, 13
Ishioka, Kunie
Wednesday 16:00, 58
Kachel, Torsten
Monday 19:30, 34
Tuesday 11:00, 42
Tuesday 11:20, 43
Wednesday 19:30, 76
Kampa, Daniel
Wednesday 19:30, 79
Kampfrath, Tobias
Thursday 11:20, 85
Kaplan, Andrey
Monday 19:30, 36
Kapteyn, Henry
Wednesday 11:20, 50
Wednesday 12:00, 51
Wednesday 12:20, 52
Katsnelson, M.
Tuesday 11:20, 43
Kawai, Maki
Monday 18:00, 19
Kiel, Mario
Wednesday 19:30, 69
Kim, Ki Hyun
Monday 19:30, 32
Kim, Seong Keun
Wednesday 19:30, 74
King, David A.
Monday 19:30, 28
Kirchmann, Patrick S.
Monday 19:30, 37
Wednesday 19:30, 64
Thursday 11:00, 84
Kirschner, Jürgen
Monday 18:30, 20
Wednesday 19:30, 70, 72
97
Author Index
Kitajima, Masahiro
Wednesday 17:50, 61
Köhler, W.
Monday 19:30, 100
Kopprasch, Jens
Monday 19:30, 35
Krausz, F.
Monday 19:30, 100
Krausz, Ferenz
Wednesday 9:00, 47
Krenz, Marcel
Thursday 11:00, 84
Krenzer, B.
Monday 19:30, 31
Thursday 15:20, 90
Kubo, A.
Thursday 18:20, 95
Kübler, Carl
Thursday 9:00, 82
Kusmierek, Daniela O.
Monday 19:30, 23
Kwon, Hyuksang
Wednesday 19:30, 74
Lane, Ian M.
Monday 19:30, 28
La-o-vorakiat, Chan
Wednesday 12:20, 52
Lee, Jaedong
Monday 19:30, 29
Leitenstorfer, Alfred
Thursday 9:00, 82
Lenner, Miklos
Monday 19:30, 36
Leuenberger, Dominik
Wednesday 19:30, 77
Lichtenstein, A.
Tuesday 11:20, 43
Lin, Wen-Chin
Monday 18:30, 20
Wednesday 19:30, 70, 72
Lindenblatt, Michael
Monday 14:40, 15
Link, O.
Wednesday 11:00, 49
Lisowski, Martin
Monday 19:30, 100
Tuesday 11:20, 43
Liu, Y.
Wednesday 11:00, 49
Loukakos, Panagiotis
Thursday 11:20, 85
Lu, D.

Author Index
Thursday 11:00, 84
Lugovoj, E.
Wednesday 11:00, 49
Malvestuto, Marco
Wednesday 19:30, 78
Marangos, Jonathan P.
Monday 19:30, 36
Marks, Manuel
Monday 12:00, 12
Wednesday 19:30, 73
Mathias, Stefan
Wednesday 12:00, 51
Wednesday 12:20, 52
Wednesday 12:40, 53
Wednesday 19:30, 66
Matsumoto, Yoshiyasu
Wednesday 14:40, 55
Matsuo, Jiro
Wednesday 19:30, 71
Melnikov, Alexey
Monday 19:30, 34
Tuesday 11:00, 42
Tuesday 11:20, 43
Wednesday 19:30, 80
Melzer, Andrea
Wednesday 19:30, 79
Menzel, Dietrich
Monday 19:30, 32
Meyer, Michael
Monday 19:30, 23, 26
Meyer zu Heringdorf, F.-J.
Thursday 16:20, 92
Miaja-Avila, Luis
Wednesday 12:00, 51
Wednesday 12:20, 52
Miller, R. J. Dwayne
Thursday 14:40, 89
Miyakubo, K.
Thursday 17:20, 93
Miyamoto, Yoshinobu
Wednesday 16:20, 59
Möllenbeck, S.
Thursday 15:20, 90
Thursday 16:20, 92
Möllenbeck, Simone
Monday 19:30, 31
Moore, R. G.
Thursday 11:00, 84
Morgenstern, Karina
Sunday 17:40, 5
Munakata, Toshiaki
Thursday 17:20, 93
Muntwiler, Matthias
Monday 16:00, 17
Monday 19:30, 24
Murnane, Margaret
Wednesday 11:20, 50
Wednesday 12:00, 51
Wednesday 12:20, 52
Nagasono, Mitsuru
Wednesday 19:30, 80
Nojima, Akihiro
Monday 11:00, 10
Norris, David J.
Wednesday 19:30, 68
N´yvlt, Miroslav
Wednesday 19:30, 72
Olsson, Fredrik E.
Monday 11:20, 11
Wednesday 19:30, 65
Osterwalder, Jürg
Wednesday 19:30, 77
Palmer, Richard E.
Monday 19:30, 36
Panzer, Ilja
Monday 19:30, 33
Park, Juyeon
Wednesday 19:30, 74
Parmigiani, Fulvio
Wednesday 19:30, 78
Pehlke, Eckhard
Monday 14:40, 15
Pelka, T.
Monday 19:30, 31
Thursday 15:20, 90
Perfetti, Luca
Thursday 11:00, 84
Thursday 11:20, 85
Petek, Hrvoje
Monday 18:30, 20
Wednesday 16:00, 58
Wednesday 17:50, 61
Wednesday 19:30, 70, 72
Thursday 18:20, 95
Pfeiffer, Walter
Monday 19:30, 38
Thursday 15:40, 91
Pickel, Martin
Monday 19:30, 33
Tuesday 11:50, 44
Pietzsch, Annette
Wednesday 19:30, 80
Pontius, Niko
Monday 19:30, 34
98
Tuesday 11:00, 42
Tuesday 11:20, 43
Wednesday 19:30, 76
Poppe, A.
Monday 19:30, 100
Prima-Garcia, Helena
Tuesday 11:20, 43
Radu, Ilie
Wednesday 19:30, 76
Ramm, P.
Wednesday 19:30, 76
Raschke, Markus B.
Wednesday 17:20, 60
Rasing, Theo
Tuesday 12:20, 45
Raß, N.
Thursday 16:20, 92
Reinert, Friedel
Monday 12:00, 12
Rettig, Laurenz
Monday 19:30, 37
Wednesday 19:30, 64
Thursday 11:00, 84
Robinson, Joseph S.
Monday 19:30, 36
Rohleder, Marcus
Monday 19:30, 30
Rohmer, Martin
Monday 19:30, 38
Rohwer, Timm
Wednesday 19:30, 66
Rosenfeldt, Arne
Wednesday 19:30, 75
Ru, N.
Thursday 11:00, 84
Rubio, Angel
Wednesday 16:00, 58
Rügheimer, Tilman K.
Monday 19:30, 22
Ruffing, Andreas
Wednesday 12:00, 51
Rutkowski, Marco
Wednesday 15:40, 57
Ryu, Sunmin
Wednesday 19:30, 74
Saathoff, Guido
Wednesday 12:20, 52
Sachs, Sönke
Monday 12:00, 12
Schäfer, Hanjo
Monday 19:30, 25
Scheuch, Martin

Thursday 11:20, 85
Schmidt, Anke B.
Monday 19:30, 33
Tuesday 11:50, 44
Schmidt, Roland
Monday 19:30, 27
Tuesday 11:20, 43
Schmitt, F.
Thursday 11:00, 84
Schneider, Christian
Monday 19:30, 38
Schneider, P.
Monday 19:30, 31
Thursday 15:20, 90
Schöll, Achim
Monday 12:00, 12
Schönhammer, Kurt
Thursday 9:40, 83
Schubert, Kai
Wednesday 19:30, 67, 73
Schwalb, Christian
Monday 12:00, 12
Wednesday 19:30, 73
Seddon, Elaine A.
Wednesday 19:30, 78
Seideman, Tamar
Thursday 17:40, 94
Shen, Z.-X.
Thursday 11:00, 84
Shibuta, M.
Thursday 17:20, 93
ˇSiber, Antonio
Thursday 12:00, 86
Siefermann, K.
Wednesday 11:00, 49
Siegmann, Hans C.
Tuesday 9:00, 40
Siemer, Björn
Wednesday 15:40, 57
Sovago, Maria
Wednesday 18:20, 62
Städter, David
Monday 19:30, 25
Stähler, Julia
Monday 19:30, 23, 26
Stamm, Christian
Monday 19:30, 34
Tuesday 11:00, 42
Tuesday 11:20, 43
Wednesday 19:30, 76
Steeb, Felix
Monday 19:30, 38
Wednesday 12:40, 53
Stöhr, Joachim
Tuesday 9:00, 40
Strüber, Christian
Monday 19:30, 38
Sukharev, Maxim
Thursday 17:40, 94
Sultan, Muhammad
Tuesday 11:00, 42
Tuesday 11:20, 43
Takagi, Noriaki
Monday 18:00, 19
Tanimura, Katsumi
Monday 12:40, 13
Monday 15:20, 16
Tempea, G.
Monday 19:30, 100
Thewes, Carsten
Wednesday 15:40, 57
Thiele, J. U.
Wednesday 19:30, 76
Tisch, John W. G.
Monday 19:30, 36
Tisdale, William A.
Monday 16:00, 17
Monday 19:30, 24
Wednesday 19:30, 68
Tomeljak, Andrej
Monday 19:30, 25
Tominaga, Junji
Wednesday 16:20, 59
Uehara, Yoichi
Monday 18:00, 19
Umbach, Eberhard
Monday 12:00, 12
Ushioda, Sukekatsu
Monday 18:00, 19
van Heys, Jan
Monday 14:40, 15
Vlaic, Sergio
Wednesday 19:30, 78
Vöhringer-Martinez, E.
Wednesday 11:00, 49
Voronine, Dmitri V.
Monday 19:30, 38
Wang, Jinxiong
Wednesday 19:30, 79
Watanabe, Kazuo
Monday 19:30, 32
Watanabe, Kazuya
Wednesday 14:40, 55
99
Author Index
Weber, Ramona
Tuesday 11:20, 43
Wehling, T.
Tuesday 11:20, 43
Weinelt, Martin
Monday 19:30, 27, 33–35
Tuesday 11:00, 42
Tuesday 11:20, 43
Tuesday 11:50, 44
Widdra, Wolf
Wednesday 19:30, 69
Wiesenmayer, Martin
Wednesday 12:00, 51
Wednesday 19:30, 66
Wietstruk, Marko
Monday 19:30, 34
Tuesday 11:00, 42
Tuesday 11:20, 43
Winkelmann, Aimo
Monday 18:30, 20
Wednesday 19:30, 70, 72
Wirtz, Ludger
Wednesday 16:00, 58
Wolf, Martin
Sunday 17:00, 4
Monday 19:30, 23, 26, 37
Wednesday 15:20, 56
Wednesday 19:30, 64, 80
Thursday 11:00, 84
Thursday 11:20, 85
Wurth, Wilfried
Wednesday 19:30, 80
Wednesday 9:40, 48
Yamada, T.
Thursday 17:20, 93
Yamamoto, Mayuko
Monday 18:00, 19
Yamamoto, R.
Thursday 17:20, 93
Yamashita, Koichi
Monday 11:00, 10
Yang, Qingxin
Monday 16:00, 17
Yin, Jing
Wednesday 12:20, 52
Zacharias, Helmut
Wednesday 15:40, 57
Wednesday 19:30, 75
Zhu, Xiaoyang
Monday 16:00, 17
Monday 19:30, 24
Wednesday 19:30, 68

Advances in ultrafast surface spectroscopies 19:30
Poster Monday 19:30
Femtosecond Ti:Sa chirped pulse oscillator
MARTIN LISOWSKI 1 , W. KÖHLER 1 , G. TEMPEA 1 , A. FERNANDEZ 2 , T. FUJI 3 , A. POPPE 2 , A.
FÜRBACH 4 , F. KRAUSZ 5 , and A. APOLONSKIY 5
1 FEMTOLASERS Produktions GmbH, Fernkorngasse 10, 1100 Wien, Austria
2 Photonics Institute, TU Wien, Gusshausstr. 27, 1040 Wien, Austria
3 Chemical Dynamics Laboratory, RIKEN, Wako, Japan
4 Physics Department, Macquarie University, New South Wales, Australia
5 Max-Planck-Institut für Quantenoptik, Garching, Germany
martin.lisowski@femtolasers.com
We demonstrate a chirped pulse Ti:Sa oscillator with 45 fs pulses at > 500 nJ pulse energy
and 5.2 MHz repetition rate. After generation of a white-light continuum in a sapphire plate
dispersive mirrors can be used to compress the continuum to 14 fs FWHM.
100

W18 Advances in ultrafast surface spectroscopies
Poster Wednesday 19:30
250 kHz, sub-40 fs pulses from a compact Ti:S regenerative CW-pumped
amplifier
ALEXANDER SCHILL, MICHAEL STEINER-SHEPARD, BOJAN RESAN, ALAN FRY, MARCO
ARRIGONI, and STEVE BUTCHER
Coherent Inc., 5100 Patrick Henry Drive, Santa Clara, CA 95054, USA
Hans-Ulrich.Emmerichs@Coherent.com
Most conventional CPA systems operate in the 1-10 kHz region and generate milliJoule pulses.
Because most experiments in bulk or at the interfaces of condensed-phase samples can be fulfilled
with microJoule pulses, a laser source generating this energy per pulse at a higher repetition rate
offer the benefits of a reduction in the data acquisition time by a factor 25-100. So far available
sources at 250 kHz were limited to performance in the 50-60 fs range. In this poster we described
several technology improvements that allow the generation of 30 fs pulses from a 250 KHz Ti:S
amplifier in very compact package. Key elements of the design of this system are a 100 nm
integrated seed laser including also the CW pump of the CPA system, an improved stretcher
compressor assembly and the use of a Spatial Modulator for pulse management and optimization.
The use of CW pumping in conjunction with an extremely low-noise pump laser is key to achieve
optimum low noise operations.
101