Diabatic energy level confluence: The mechanism of negative ion conversion of neutral atoms in grazing scattering from insulator surfaces

The mechanism mediating electron transfer from an alkali halide surface to an atom by bringing diabatically the relevant atomic and surface energy levels into near resonance is elucidated. The mechanism is supported by parameter free calculations on a model F/LiF(100) system where all sites of the crystal lattice but one, the active site, are represented by (polarizable) point charges. The electron transfer interaction between the atom and the active F site of the surface is computed and used in dynamics calculations of negative ion formation in a sequence of binary collisions.