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

Total electron yields have been determined from electron emission stat istics 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 energ ies have been varied from almost zero up to 10 X q keV. The obtained t otal electron yields deviate considerably from available data derived via ion- and electron current measurements for LiF single crystal targ ets. Our results are explained by comparison with a recent model for M Cl induced potential electron emission from clean metal surfaces, whic h has been properly adapted, available theory for kinetic electron emi ssion from alkalihalide surfaces, and by considering also measured sec ondary electron yields for LiF. Dependences of the electron emission s tatistics and -yields on projectile impact energy and -charge differ s trongly from corresponding properties for clean metal surfaces, which can be explained from the different roles of potential- and kinetic em ission and, in particular, a relatively stronger contribution from sec ondary electron emission induced by fast electrons from finally neutra lising projectiles inside the LiF bulk.