Negative-ion conversion of fluorine atoms in grazing scattering from a LiF(001) surface: A coupled cluster approach

The F^- ion formation from fluorine atoms in grazing scattering from a LiF(001) surface is studied. The coupled cluster treatment of the LiF target allows one to take into account the possible effect of the finite width of the valence band of the crystal on the negative-ion formation. The finite width of the valence band implies that the hole created in the crystal by electron transfer to the projectile can a priori migrate out of the charge transfer region thus promoting the negative-ion formation. We find that while for the perfect crystal the hole diffusion is rather fast, in the case of a collision, it is temporarily suppressed by the attractive Coulomb interaction between the hole and the negative ion in the final state of the charge transfer reaction. As a result, the charge transfer has a ``localized'' character and corresponds to binary-type electronic transitions between the projectile and the closest lattice sites along the trajectory.