Long-range excitation of electron-hole pairs in atom-surface scattering

The van der Waals potential of a neutral atom at rest outside a metal surface is a consequence of virtual excitations of the substrate and of the atom. If the atom is moving the van der Waals potential becomes complex, the imaginary part corresponding to real excitations of the substrate, e.g. excitation of electron-hole pairs on surface plasmons. Using a self-energy formulation of this complex van der Waals interaction we derive expressions for inelastic scattering probabilities of atoms or ions reflected from surfaces. In the case of ion scattering from surfaces this reproduces a well known result. For neutral atom scattering we calculate inelastic scattering probabilities for xenon atoms incident on metal surfaces at hyperthermal energies. We compare our results with the recent experiments of Amirav and Cardillo. 16 refs