Interaction of molecular hydrogen ions with the LiF(100) surface

Scattering of H₂⁺ molecules from a LiF(100) surface at grazing incidence is studied in the energy range from 600 to 4000 eV. The scattered particle yield measured in an azimuthal scan at various temperatures showed peaking at the [1¯00] direction. A W-shaped peaked yield was observed near the [1¯00] direction above a temperature of about 200°C, which shows that there is no charging up of the LiF crystal at this temperature. About 70% molecular survival was obtained at a very low primary energy of about 600 eV and this dropped to about 20% around 1300 keV. At low H₂⁺ energies a very low charge state fraction H⁺ and H^- ions were observed and it reached a maximum to about 15%, and 10%, respectively, around 2-2.5 keV and decreased at higher energies. The molecular survival fraction and the charge state fractions stabilize above 250°C. The molecular survival fraction was found to be higher at a random condition when compared to the yield at the [1¯00] axis. The mean energy loss of the neutral atoms is found to increase linearly with energy.