Observation of skipping motion or transient adsorption in small angle scattering of silicon ions from a Cu(111) surface

Transient adsorption or skipping motion of 200-2000 eV silicon ions scattered under specular conditions from a Cu(111) surface is reported. The phenomena are identified on the basis of the observation of discrete energy loss peaks in the scattered Si+ and Si- ion kinetic energy distributions, together with their behaviour upon variation of the crystal azimuth, incidence angle of the beam to the surface, and scattering angular distributions. Up to five reflections, with a total energy loss of 20% of the incident beam energy, could be identified. We propose that the beam is trapped following energy loss, by electron-hole pair and plasmon excitation, which exceeds the incident bean energy component normal to the surface. Trajectory calculations which include this coupling of the energy loss and interaction potential satisfactorily reproduce the experimental observations. (author)