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.

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Two electrons, excited just above the double-ionization threshold of an Ag + (q =5,6) core in a single collision of a 0. 1-MeV/u Ag + projectile ion with an Ar atom, are detected. The electron detector consists of electrically isolated anode segments located behind a microchannel-plate electron multiplier. A large electrostatic 30 parallel-plate analyzer is used to deAect the two free electrons, which move with approximately the projectile velocity, into the detector. The cross sections for producing final states consisting of a positively charged ionic core and two electrons just above the threshold for double ionization in ion-atom collisions have been measured. The cross sections for producing states with one electron moving with a kinetic energy less than 0.13 eV in the projectile frame and the other moving with somewhat higher kinetic energy are presented.PACS number(s): 34.50.Fa