Image charge attraction of multicharged Xe-ions in front of insulator surfaces

Multicharged Xe-q+-ions (q < 20) are scattered with keV energies under a grazing angle of incidence from the surface of two different insulators: LiF(100) and KI(100). From the analysis of angular distributions for scattered projectiles we deduce energy gains caused by the dielectric response of the target material due to the presence of the external charge (''image charge interaction''). A direct comparison of the interaction energies gained by the projectiles on the incident path with the two different targets is consistent with the assumption of a dominant population of Rydberg levels (''hollow atom'') in front of insulators for grazing ion-surface scattering.