Quantum model for kinetics of helium atoms near surfaces of free-electron metals: II. Overlap-induced dissipation

Abstract

A quantum model developed formerly to describe inelastic collisions of low-energy helium atoms with surfaces of free-electron metals is extended to include the electronically induced dissipative scattering arising from the overlap-induced electron-helium atom pseudopotential. It is shown that the repulsive adatom-substrate Hartree-Fock interaction, known from the work of Zaremba and Kohn to be proportional to the overlap S between the adatom and substrate electronic densities, is succeeded by a series of nonadiabatic higher-order terms which also give rise to dissipative processes in adatom-surf ace collisions. The leading contribution to this series which contains the information on the decay rate of the adparticle initial state is calculated up to the order S 2 using the formalism of the surface response function developed earlier. Such a formulation does not require the use of any adjustable parameters and the results obtained indicate the importance of this scattering mechanism with respect to the polarization-induced dissipation discussed in Part I [Surface Sci. 117 (1982) 116].