POSITION-DEPENDENT CHARGE-EXCHANGE AND ENERGY-LOSS PROCESSES FOR MEV HE IONS NEAR A CRYSTAL-SURFACE

Inelastic interaction Of fast ions at glancing angles of incidence on a low index crystal surface is described by the probabilities, which d epend on the distance of the ion from the surface; the charge state an d energy distributions of the scattered ions are found to result from position-dependent interactions along their trajectories in vacuum. A stochastic equation to describe the charge exchange and energy loss of specularly reflected ions is proposed. Taking account of ion scatteri ng at surface steps, the theory is applied to derive the position-depe ndent probabilities of electron loss and electron capture of MeV ions from the observed charge state and energy distributions of the scatter ed ions at glancing angle incidence on the (100) surface of SnTe.