Charge state distribution after the scattering of fast He~+-ions from an Al (111)-surface under a grazing angle of incidence

摘要

He~+-ions with energies from 3 keV to 1.4 MeV are scattered from a clean and flat Al(111)-surface under a grazing agle of incidence, and the scattered projectiles are analyzed with respect to charge states. We observe defined kinematic thresholds for the formation of He~+-as well as of He~2+-ions which are in agreement with the onset of a kinematically induced Auger-ionization process, Comparison of our data with foil transmission experiments shows a clearly different dependence of the charge state fractions on the promectile energy (velocity).