Electron capture and loss processes in the interaction of hydrogen, oxygen, and fluorine atoms and negative ions with a MgO(100) surface

A study of electron capture and loss processes during the scattering of H, O, and F atoms and anions on a MgO(100) surface is described. Large fractions of anions in the scattering of atoms are observed, indicating the existence of an efficient electron capture process. This is ascribed to a nonresonant, localized charge exchange mechanism between an atom and a MgO lattice oxygen anion. This charge transfer becomes possible because of anion level shifts in the Madelung field. The existence of an electron loss channel is demonstrated using incident anions and is ascribed to loss to the conduction band or Mg cations.