Energy loss of charged particles interacting with simple metal surfaces

Self-consistent calculations of the energy-loss spectra of charged particles moving near a plane-bounded free electron gas are reported. Energy-loss probabilities are obtained, within linear-response theory, from the knowledge of the density-response function of the inhomogeneous electron system. Self-consistent single-particle wave functions and energies are obtained by solving the Kohn-Sham equation of density-functional theory, and the electronic response is then computed either in the random-phase approximation or with the use of an adiabatic local-density approximation. Special emphasis is placed on the various contributions from collective and electron-hole excitations to the energy loss of charged particles moving parallel with the surface. The effect of the electronic selvage at a metal surface on the energy-loss spectra is also discussed, by comparing our full self-consistent calculations with those obtained for electron densities that drop abruptly to zero at the surface.