Regensburg 2007 – scientific programme
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O: Fachverband Oberflächenphysik
O 32: Semiconductor Substrates
O 32.5: Talk
Tuesday, March 27, 2007, 16:45–17:00, H39
Identifying isomerization - combined experimental and theoretical NEXAFS studies — •Philipp Martin Schmidt1, Ralph Püttner2, Christine Kolczewski1, Klaus Hermann1, Karsten Horn1, and Thorsten Kampen1 — 11 Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin, Germany — 2Freie Universität Berlin, Institut für Experimentalphysik, Berlin, Germany
When studying the isomerization of molecules, identification and distinction of the different isomers is a critical issue. Here cis- and trans-Stilbene are a model system for "molecular switches". We have investigated their adsorption on Si(100) and Au(111) surfaces, and for comparison, in gas-phase. In this work we demonstrate the use of NEXAFS-spectroscopy as a versatile tool to investigate the interaction of the molecules with the surface and the arising consequences for isomerization. NEXAFS-spectra of the molecules in gas-phase show spectral features in the π*-resonance that allow for a clear distinction of the isomers. Upon adsorption on surfaces these spectral features remain unchanged - thus clearly identifying the isomers - while the σ*-resonances and the higher π*-resonances undergo changes. In combination with theoretical calculations these changes can be used to identify the interaction of the molecules with the substrates and to reveal the adsorption geometry. Furthermore the implication of adsorption on the photoinduced isomerization, especially the inhibition of the isomerization-pathways known for gas-phase and solution, is explained.