Negative-ion formation by H0/H– projectiles grazing scattering from the MgO(100) surface

Abstract

A simple theoretical model used to treat the formation of negative ions during ${\mathrm{H}}^{--}/{\mathrm{H}}^{0}$ grazing scattering from the MgO(100) surface is presented. It is revealed that the resonant transfer from projectiles to the conduction band and the detachment of tunneling Coulomb repulsive barrier to the vacuum of the affinity electron of ${\mathrm{H}}^{--}$ ions both play an important role in the electron-loss processes. The negative-ion destruction is dominated by a nearly resonant electron loss in the low projectile energy region of $E\ensuremath{\le}0.7\phantom{\rule{0.16em}{0ex}}\mathrm{keV}$ (velocities $v\ensuremath{\le}0.17\phantom{\rule{0.16em}{0ex}}\mathrm{a}.\phantom{\rule{0.16em}{0ex}}\mathrm{u}.$), whereas the detachment by Coulomb repulsive barrier tunneling during the interaction between projectiles and surface anion sites becomes efficient in the high-energy region of $E\ensuremath{\ge}1.2\phantom{\rule{0.16em}{0ex}}\mathrm{keV}$ ($v\ensuremath{\ge}0.22\phantom{\rule{0.16em}{0ex}}\mathrm{a}.\phantom{\rule{0.16em}{0ex}}\mathrm{u}$). Combined with the valence-band electron capture, our present calculation results of the negative ion yields are in good agreement with the available experimental data in the whole velocity region.