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Surface Femtochemistry

Electron Dynamics
Surface Femtochemistry

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Prof. Dr. Martin Wolf
Abt. Physikalische Chemie
Fritz-Haber Institut der MPG
Faradayweg 4-6
14195 Berlin, Germany
phone:+49 30 8413-5111
Fax: +49 30 8413-5106

hitherto (2010):
Department of Physics
Free University Berlin
Arnimallee 14
D - 14195 Berlin

Surface femtochemistry

Optical excitation of metals with intense femtosecond laser pulses can create extreme non-equilibrium conditions in the solid. The electronic system reaches several thousand degrees Kelvin on a sub-picosecond time scale while the lattice (phonon bath) stays fairly cold. Such photoexcited hot electrons may transiently attach to unoccupied adsorbate levels and this change in the electronic structure may induce vibrational motions of the adsorbate substrate bond (see diagram below). For high excitation densities with femtosecond pulses, multiple excitation/deexcitation cycles can occur and may eventually lead to desorption of adsorbate molecules or reactions with co-adsorbed species.
After 1-2 ps the hot electron distribution equilibrates with the lattice and the heated phonon bath may induce chemical reactions by thermal activation. Time-resolved experiments with a pair of two excitation pulses allow distinction between phonon or electron driven mechanisms and provide insight into the rate and pathways of energy flow in surface chemistry.

CO Oxidation | SFG Exp. Setup | Cluster Exp. Setup | Overview

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