ELECTRON-EMISSION FROM POLYCRYSTALLINE LITHIUM-FLUORIDE BOMBARDED BY SLOW MULTICHARGED IONS

Total electron yields have been determined from electron emission statistics measured for impact of H+, N-q+ (q = 1, 5, 6) and Ar-q+ (q = 1, 3, 6, 9) On clean, polycrystalline lithium fluoride. Ion impact energies have been varied from almost zero up to 10 X q keV. The obtained total electron yields deviate considerably from available data derived via ion- and electron current measurements for LiF single crystal targets. Our results are explained by comparison with a recent model for MCl induced potential electron emission from clean metal surfaces, which has been properly adapted, available theory for kinetic electron emission from alkalihalide surfaces, and by considering also measured secondary electron yields for LiF. Dependences of the electron emission statistics and -yields on projectile impact energy and -charge differ strongly from corresponding properties for clean metal surfaces, which can be explained from the different roles of potential- and kinetic emission and, in particular, a relatively stronger contribution from secondary electron emission induced by fast electrons from finally neutralising projectiles inside the LiF bulk.