Semiclassical treatment of reactions at surfaces with electronic transitions

The semiclassical treatment of reactions at surfaces with electronic transitions based on the fewest-switches algorithm is compared with full quantum mechanical results. As a model system the ionization probability in I-2 scattering from a diamond surface is chosen. In the calculations we treat the molecular distance from the surface and one surface oscillator coordinate explicitly. Furthermore, we also consider molecular rotation in the semiclassical calculations. The semiclassical results agree with the quantum results although some discrepancies remain, as far as the phase coherence is concerned. We identify energy transfer to molecular and surface degrees of freedom as a possible mechanism that could explain the experimental dependence of the ionization probability on the incident kinetic energy of the molecule.