Charge Exchange between singly charged Ions and a LiF surface

In recent years the interaction of ions with insulator surfaces has attracted increased interest. The system is sketched in Fig. 1: a positively charged ion approaches a LiF-surface and may be neutralized by transfer of electrons from the surface. Contrary to metal surfaces, electron transfer to the projec-Figure 1: Sketch of a positive ion approaching a LiF surface tile ion can lead to a local charging up of the surface. Through self-trapping of electronic defects, the recombination energy of the projectile ion (i. e. the potential energy that the ion carries into the collision with the surface) can be converted into kinetic energy of surface atoms and lead to the ablation of secondary particles from the surface. This process is called potential sputter-ing (PS) and has to be distinguished from the well known process of kinetic sputtering (KS), where the removal of surface atoms/ions is due to the kinetic energy of the projectile. PS with very slow ions offers the possibility for con-trolled modification of the surface layer without radiation damage to deeper layers. PS has been observed for a variety of insulator surfaces with stron