Autoionising state excitation in collisions of inert gas projectiles with an Al surface and effects of initial stages of oxidation

Results of an angle resolved electron spectroscopy study of low keV He⁺, Ne and Ne⁺ collisions with an Al surface are presented. Production of projectile autoionising states is demonstrated to exist not only for the previously known Ne⁺ case but also for Ne and He⁺. The characteristics of autoionising peak line shapes suggest differences in angular distributions of the different Ne^** states. Initial stages of the oxidation of Al are studied. Saturation coverages of oxygen are reached for exposures greater than 100 L. An initial decrease in the work function is observed amounting to 160 meV for a 30 L exposure. Exposure to oxygen results in a strong decrease of autoionising state production. State-selective attenuation is observed and reflects changes in electron transfer rates.