Formation of negative ions in grazing scattering from insulator surfaces

Substantial fractions of fast atoms or ions are converted to negative ions during grazing scattering from a clean and flat monocrystalline surface of alkali-metal halides. We interpret the experimental data by a model of local electron capture from the halogen sites of the crystal in binary-type collision events. Due to the band gap of the insulator, the probability far subsequent electron loss is low, resulting in large fractions of negative ions that survive from the collisional formation. [S1050-2947(98)01201-3].