Backward ejected electrons produced by 1-MeV/u Oq+ (q=3-8) projectile ions colliding with argon gas.

Abstract

The cross sections for ejecting electrons into a cone of half-angle [similar to]2[degree] centered on the backward direction have been measured as a function of electron energy for 1-MeV/u O[sup [ital q]+] ([ital q]=3--8) projectiles colliding with Ar. For O[sup 3+] and O[sup 4+] projectiles, the cross sections have also been measured in coincidence with exit charge states ([ital q]+1) and ([ital q]+2) of the projectile. A prominent feature in all spectra is a target [ital LMM] Auger peak. The cross sections for producing Ar [ital LMM] Auger electrons are nearly independent of projectile incident charge states. A projectile electron-loss peak is produced when the projectile brings loosely bound [ital L]-shell electrons into the collision. The shape of this peak is independent of the projectile exit charge state within experimental error. The measured electron-loss production cross sections at 180[degree] are compared with the predictions of various on-shell approximations to the impulse approximation. Peak height and position are sensitive functions of the on-shell approximation used. The predictions of the elastic scattering model agree well with the data.