Trajectory-dependent energy loss for swift He atoms axially scattered off a silver surface

Abstract

Angle-and energy-loss-resolved distributions of helium atoms grazingly scattered from a Ag(110) surface along low indexed crystallographic directions are investigated considering impact energies in the few keV range. Final projectile distributions are evaluated within a semi-classical formalism that includes dissipative effects due to electron-hole excitations through a friction force. For monoenergetic beams impinging along the [110], [112] and [110] directions, the model predicts the presence of multiple peak structures in energy-loss spectra. Such structures provide detailed information about the trajectory-dependent energy loss. However, when the experimental dispersion of the incident beam is taken into account, these energy-loss peaks are completely washed out, giving rise to a smooth energy-loss distribution, in fairly good agreement with available experimental data.

Grazing incidence fast atom and molecule diffraction: theoretical challenges

“…The inelastic contribution due to electronic excitations in the crystal can be assumed as completely incoherent 154 because such electronic transitions allow one to trace back the projectile pathways. 169 Thence, in ref. 163 this contribution was evaluated by means of a semiclassical formalism that takes into account the energy lost by the projectile along the classical trajectory, but without including effects of quantum coherence.…”