The cross sections for ejecting electrons into a cone of half-angle -2' centered on the backward direction have been measured as a function of electron energy for 1-MeV/u Oq+ (q =3-8) projectiles colliding with Ar. For 0'+ and 0 + projectiles, the cross sections have also been measured in coincidence with exit charge states (q +1) and (q +2) of the projectile. A prominent feature in all spectra is a target LMM Auger peak. The cross sections for producing Ar LMM Auger electrons are nearly independent of projectile incident charge states. A projectile electron-loss peak is produced when the projectile brings loosely bound 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 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.
The energy of the binary-encounter peak has been determined for 0.6 MeV/u O, F, Si, Ti, Cu, and Br ions colliding with H 2 targets. The projectiles all had the same charge qϭ7, while the atomic number Z of the projectiles ranged from 8 ͑almost totally ionized͒ to 35 ͑retaining 28 electrons͒. We observe that the binaryencounter-peak energy for fixed q increases as Z increases. This trend is opposite to that observed when Z is fixed and the charge q is varied, and it demonstrates that the binary-encounter-peak energy depends not only on the net projectile charge but on the projectile core as well. The experimental trend is qualitatively reproduced by an impulse approximation showing that this variation in the binary-encounter-peak energy may be attributed to the effect that the projectile core potential has on the electron elastic-scattering cross section.
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