Energy loss of H+ fragments arising from dissociation of fast H2+ ions under glancing-angle incidence on a SnTe(001) surface

Energy losses of H+ fragments repelled parallel and antiparallel to the beam direction at dissociation are measured for a glancing-angle incidence of 0.15-0.6-MeV/amu H2+ ions on a clean (001) surface of SnTe. The sum of the energy losses of the specularly reflected fragments is larger than twice that of protons of the same velocity reflected from the surface. For the interpretation of the vicinage effect on the stopping power of the surface, the energy losses of the pairs of fragments resulting from the dissociation of H2+ are calculated at the glancing-angle scattering. The contribution of single-electron excitation to the energy loss of the pair is calculated with the harmonic-oscillator model [J.Basbas and R.H.Ritchie, Phys. Rev. A 25, 1943 (1982)] and that of collective excitation by the superposition of surface wakes of two protons. A dependence of the vicinage effect on the distance from the surface is found from the calculated stopping powers, where the pronounced effect becomes weak as the distance decreases. The calculated energy losses of the reflected pairs of protons agree fairly with those measured. The agreement of the calculated energy losses with those measured supports the calculated dependence of the vicinage effects. [S1050-2947(97)0781O-4