Dresden 2006 – wissenschaftliches Programm
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O: Oberflächenphysik
O 14: Poster session I (Adsorption, Epitaxy and growth, Phase transitions, Surface reactions, Organic films, Electronic structure, Methods) (sponsored by Omicron Nanotechnology GmbH)
O 14.36: Poster
Montag, 27. März 2006, 18:00–21:00, P2
Activated associative desorption: CO recombination driven by hot electrons — •Steffen Wagner1, Marcel Krenz1, Alexander Kaebe1, Christian Frischkorn1, Martin Wolf1, and Alan Luntz2 — 1Freie Universität Berlin — 2University of Southern Denmark, Odense
The formation and desorption of molecular CO from atomic carbon and oxygen bound to a Ru(001) surface have been investigated femtosecond-laser irradiation. A strong non-linearity in the desorption yield with respect to the applied laser fluence and a narrow two-pulse correlation (2PC) width indicate an electron-mediated reaction mechanism. Surprisingly, measurements of the translational energy of the desorbing CO molecules show almost no dependence on the applied laser fluence. The origin of these findings is attributed to the shape of the potential energy surface where along the reaction pathway a high barrier (∼1.8 eV) and a deep chemisorption well (∼0.8 eV) have to be traversed. We assign the fluence independent translational energy to a thermalization of the nascent molecules in the chemisorption well. Experiments employing time-resolved vibrational spectroscopy via sum-frequency generation on the CO stretch vibration are underway and will give further insight into this reaction.