Untitled - IAP/TU Wien - Technische Universität Wien

71st IUVSTA Workshop
Plasmon resonant (e,2e) spectroscopy
A. Ruocco a , W. S.M. Werner b , M.I. Trioni c , F. Offi a , S. Iacobucci d , W. Smekal b
G. Di Filippo e and G. Stefani a
a Dipartimento di Scienze
b , Vienna University of Technology, Vienna,
Austria
c CNR, Istituto di Scienze e Tecnologie Molecolari (ISTM), Milan Italy
d IFN-
e
The (e,2e) process has been largely used to investigate ionization mechanisms
and electronic structure in atoms, molecules and solids. In solids, one of the
most efficient channels of electron impact energy transfer is excitation of
volume or surface plasmons (collective excitations of the electron gas). Two
main plasmon decay mechanisms have been foreseen: the excitation of nearly
free secondary electrons and the excitation of pair of correlated free electrons 1 .
In competition with these two channels, the ejection of a secondary electron due
to direct scattering within a medium described by its inverse dielectric function
has been proposed 2 .
To establish the relative relevance of these secondary electron generation
channels is of importance in many branches of fundamental and applied
science.
In this paper will be reviewed (e,2e) plasmon assisted experiments performed
on Al and Be clean surfaces. The early experiment on Al 3 , performed at 100eV
incident energy, proposes that observed secondary electrons are emitted via a
mechanism similar to photoemission with plasmon decay playing the role of
photon absorption. The experiment performed always on Al at 500 eV 4 proves
that surface plasmon decay accounts for roughly a quarter of the secondary
electron spectrum. More recent experiment on Be 5 point to plasmon resonant
(e,2e) processes as a relevant channel for secondary electron generation and
for building a resonant momentum spectroscopy.
1 G.A. Bocan and J.E. Miraglia, Phys Rev. A 71, 024901 (2005) and reference therein.
2 K.A. Kouzakov and J. Berakdar, Phys. Rev. A 85, 022901 (2012)
3 W.S.M. Werner, et al. Phys. Rev. B 78, 233403 (2008)
4 W.S.M. Werner, et al. Appl. Phys. Lett. 99, 184102 (2011)
5 A. Ruocco et al. private communication (2012)
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