ELECTRON-ELECTRON INTERACTIONS IN ION-ATOM COLLISIONS STUDIED BY ENERGY-LOSS SPECTROSCOPY

We have performed a series of experiments on the University of Missour i-Rolla ion energy-loss spectrometer to study the role of electron-ele ctron interactions in ion-atom collisions. In one experiment we have t aken energy-loss spectra for 50 keV protons colliding with He. From th e data we obtained cross sections for double excitation of the target atom. In a second experiment we measured coincidences between neutrali zed projectiles and target recoil ions in p + He collisions at project ile energies of 50 and 100 keV. From these data we obtained the ratio of transfer ionization to single capture as a function of the projecti le scattering angle. In a preliminary experiment we also used this coi ncidence technique for projectiles which did not undergo charge exchan ge and which were energy analyzed to study single and double ionizatio n.