Berlin 2012 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 12: Surface dynamics
O 12.4: Vortrag
Montag, 26. März 2012, 16:45–17:00, H 2013
Non-adiabatic Effects in the Reaction of Chlorine Molecules with Potassium — •Felix Becker, David Krix, and Hermann Nienhaus — University of Duisburg-Essen and CeNIDE, Germany
The energy released in an exothermic chemical reaction of a gas molecule with a metal surface may be dissipated adiabatically by the creation of phonons or non-adiabatically by excitation of the electronic system. In the past, non-adiabatic effects in the reaction of Cl2 with K were studied by exoelectron emission and chemiluminescence measurements only.
Here, we present XPS and chemicurrent data detecting low-energy holes as well as photons generated by the chlorination of potassium. Two kinds of large-area Schottky diodes were used as hot charge carrier detectors. The first were formed by direct deposition of K on H-terminated p-Si(111), the second had an intermediate silver layer between K and Si. For thin metal layers hot holes could be measured. They travel ballistically through the metal film and traverse the Schottky barrier if the kinetic energy is larger than the barrier height (typ. 0.4 eV). Chemiluminescence photons can be distinguished from hot holes by varying the metal film thickness as the mean free path (mfp) of the photons exceeds the mfp of hot holes. The metal film thickness dependent reverse currents strongly indicate that the presence of a rough silver film enhances the chemiluminescence during the reaction.