Sticking and inelastic scattering at metal surfaces: the influence of screening on the electron-hole pair mechanism

Abstract

A time-dependent Anderson Hamiltonian coupled to a local boson mode is used to describe screening effects in inelastic metal surface scattering. Assuming, in the spirit of the slowness approximation, that the perturbation by the approaching adsorbate is too slow to excite real plasmons, the boson degrees of freedom are removed to retain an effective purely electronic problem. The results show that, apart from the well known downward shift of the adsorbate level resonance, screening affects the shape of this resonance in a way that depends on the ratio of the two characteristic energies B (width of the substrate conduction band) and omega (plasmon frequency): for omega >>B a polaron-like renormalisation of the width is found, whereas for B>> omega the height of the resonance is reduced. The model is extended to include plasmon dispersion in a time-dependent scaling calculation.