Optical potential and escape depth for electron scattering at very low energies

Electron spectroscopy at low kinetic energies, e.g., valence band photoemis sion with vacuum ultraviolet light, is sensitive to the fine structure of t he electron damping, i.e., to the magnitude and energy dependence of the op tical potential. The basis of this quantity is usually given by a semiquant itative analytical derivation together with empirical findings from the esc ape depth. Only recently the optical potential has been determined ab-initi o via calculating the self-energy. Here, this approach is used to calculate the self-energy and from this the wave functions in the conduction band re gime with scattering boundary conditions for the surface system. For the fo rmer, the GW approximation is applied. For the latter, algebraic solvers in the Laue representation have been used to solve the Schrodinger equation f or arbitrary potentials. The wave function is investigated to extract physi cal quantities, like the angle and energy dependent escape depth, which are significant in discussing electron scattering. (C) 1999 Elsevier Science B .V. All rights reserved.