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

Scattering of ${\mathrm{H}}_{2}^{+}$ 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 $[1\ifmmode\bar\else\textasciimacron\fi{}00]$ direction. A W-shaped peaked yield was observed near the $[1\ifmmode\bar\else\textasciimacron\fi{}00]$ direction above a temperature of about $200\ifmmode^\circ\else\textdegree\fi{}\mathrm{C},$ 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 ${\mathrm{H}}_{2}^{+}$ energies a very low charge state fraction ${\mathrm{H}}^{+}$ and ${\mathrm{H}}^{\ensuremath{-}}$ ions were observed and it reached a maximum to about $15%,$ and $10%,$ respectively, around $2\ensuremath{-}2.5 \mathrm{keV}$ and decreased at higher energies. The molecular survival fraction and the charge state fractions stabilize above $250\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}.$ The molecular survival fraction was found to be higher at a random condition when compared to the yield at the $[1\ifmmode\bar\else\textasciimacron\fi{}00]$ axis. The mean energy loss of the neutral atoms is found to increase linearly with energy.

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