Probing inelastic interactions of ions moving in solids by electron spectroscopy

We have measured energy distributions of electrons emitted from clean alumi num surfaces by 20 keV/amu H+, He+ and He-0 projectiles. Ratios of energy d istributions obtained from two types of projectiles carry information on di fferences in the electron excitation collisions. We discuss these differenc es in terms of screening of the projectile by valence electrons, Auger capt ure and projectile ionization, with the aid of linear response theory. We f ind the shapes of secondary electron energy spectra are dominated by the en ergy dependence of the electron escape depth and of the binary ion-electron interaction. The latter must be determined by considering the screened pot ential of the projectile and its changing charge state as it penetrates the solid. (C) 2000 Elsevier Science B.V. All rights reserved.