Scattering of He and Ne atoms and ions on a Na surface

Abstract

Results of measurements of angular distributions of neutrals and ions in low-keV Ne + and Ne 0 collisions with a Na-covered surface are presented. These results are supplemented by time of flight measurements. Measurements of angle-resolved energy spectra of electrons are presented for He + and Ne + collisions on Na. These results are compared with those obtained on other systems (Mg, Al and Si). Ion fraction measurements show that the incident ionic projectiles are neutralized during the approach towards the surface, and then reionized due to inelastic processes occurring during binary collisions with surface atoms. Our electron spectroscopy measurements show the existence of two-electron excitation processes. These results compared with previous gas-phase results indicate the involvement of similar primary excitation mechanisms. These are well described within a diatomic quasi-molecular model. Several marked differences observed between the gas-phase measurements and our electron spectra are explained by surface specific mechanisms due to charge transfer between the projectile and the surface.