SCATTERING OF H AT NI SURFACES - CHARGE-EXCHANGE AND ENERGY-LOSS

Hydrogen is scattered at grazing incidence from Ni(111) and Ni(110) surfaces. Significant differences are found in the energy loss and the energy loss straggling as a function of the primary energy between 300 eV and 5 keV. The energy losses of the different exiting charge states H0, H+, H- for incident H+ when scattered from Ni(110) are equal, so is the energy loss straggling for H0 and H-. The straggling of exiting H+ is enhanced. The charge state fractions as a function of the particle energy agree with previous findings, i.e. the H+ yield increases with energy and the H- yield exhibits a flat maximum at about 3 keV. A theoretical model which accounts for all three charge states and reproduces the experimental findings is proposed.