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Chemische Prozesse und Phasenübergänge Vortrag: Fr., 11:50–12:10 F-V64
Surface reactions studied by in-situ x-ray photoelectron spectroscopy
Reinhard Denecke 1 , Christian Papp 1 , Barbara Tränkenschuh 1 , Thomas
Fuhrmann 1 , Regine Streber 1 , Hans-Peter Steinrück 1
1 Lehrstuhl für Physikalische Chemie II, Universität Erlangen-Nürnberg, Egerlandstr. 3,
91058 Erlangen
Employing high-flux and high-resolution synchrotron radiation from BESSY II, surface
reactions can be studied in situ using a combination of high-resolution X-ray photoelectron
spectroscopy (XPS) and a supersonic molecular beam set-up [1]. By continuously
measuring C 1s or O 1s core level spectra with total times per spectrum of only a few
seconds, surface reactions such as CO adsorption and CO oxidation with preadsorbed
atomic oxygen as well as dissociative adsorption of methane and its subsequent dehydrogenation
have been studied. From a quantitative analysis it is possible to determine
the time- and coverage-dependent occupation of different adsorption sites or the population
of certain surface species, which can be distinguished by in-situ high-resolution
XPS. This includes the identification of step and terrace species and sites on regularly
stepped surfaces [2] as well as the identification of different hydrocarbons by their specific
vibrational fine structure [3].
The majority of the experiments rely on the use of a supersonic molecular beam for
various reasons. The spatially confined beam allows for a relatively high particle flux
(equivalent to pressure) on the sample, while keeping UHV conditions in the rest of the
chamber. Secondly, the confined beam can be switched on and off precisely by a moveable
flag. Finally, activated processes, like the dissociative adsorption of methane, can
be facilitated by using highly energetic molecules provided by a supersonic molecular
beam [3].
Using all these properties, a variety of surface reactions can be studied. We will present
examples from our recent investigations.
Supported by the DFG (STE 620/4-3).
[1] R. Denecke, Appl. Phys. A 80 (2005) 977.
[2] B. Tränkenschuh, N. Fritsche, T. Fuhrmann, C. Papp, J.F. Zhu, R. Denecke,
H.-P. Steinrück, J. Chem. Phys. 124 (2006) 074712.
[3] T. Fuhrmann, M. Kinne, B. Tränkenschuh, C. Papp, J.F. Zhu, R. Denecke,
H.-P. Steinrück, New J. Phys. 7 (2005) 107.