Image Charge Acceleration of Multicharged Ions in Front of the Surface of an Insulator

Multicharged xenon ions are scattered with keV energies from a LiF(100) surface under a glancing incidence. From the angular distributions of scattered projectiles, we deduce the existence of an attractive force acting on the projectiles on the incident path. We interpret this as the dielectric response of the insulator due to the presence of an ion. The interaction energies gained on the incident trajectory are reproduced by an “overbarrier” model of stepwise capture of electrons from the fluorine $2p$ band of LiF into Rydberg levels of the projectile.