Grazing collision of keV protons on LiF correlation between energy loss and electron emission

Abstract

Grazing interaction of low energy protons with LiF(1 0 0) is studied using a new coincidence technique combining energy loss, charge state analysis and electron spectroscopy. Correlation between the scattered projectile energy loss and the number of emitted electrons points to an energy loss mechanism not leading to electron emission. Detailed analysis of the energy loss spectra, which show well-resolved structures, suggests that this mechanism corresponds to the population of surface excitons. Moreover the correlation between the projectile final charge state and the number of emitted electrons sheds new light on the major role played by the negative ion at the surface. Electron removal from the valence band proceeds mainly through formation of H − at halogen sites, whereas electron emission results from the detachment of these negative ions at subsequent F − sites.