Modeling the ion impact electron spectra from slow H+ and O+ collisions with clean and alkalated W(110) surfaces

We have modeled the ion impact electron spectra (IIES) for slow collisions (50 eV) of H+ and of ground- (S-4) and excited-state (D-2;P-2) O+ ions with W(110) surfaces, clean and partially covered by potassium, under grazing incidence. The following procedure first proposed by Niehaus et al. [1] was pursued. A set of coupled rate equations, representing the projectile in its various charge and excitation states, is solved as a function of the projectile's distance with respect to the surface. The energy spectrum is constructed from the contributions of the various Auger-type processes occuring along the projectile's trajectory. We show that, when choosing physically plausible distance-dependent rates for the involved electronic transition processes and a simple model for the projectile-surface interaction, as well as for the variation of the surface structure with alkali adsorption, very satisfying agreement of the modeled with experimental spectra can be obtained. This allows for a unique identification of all major features seen in the experimental spectra. Thus, a rather complete understanding of the dynamics of the collision is obtained in the studied cases.