Translational Inelasticity Of Hydrogen Atoms Scattering Off Hydrogen-Covered W(110) Surfaces

Quasi-classical trajectory simulations are performed to investigate the energy transfer upon scattering of hydrogen atoms off hydrogen-covered (110) tungsten surfaces. For hydrogen atoms impinging metal surfaces at energies of the order of a few electronvolts, translation energy loss has been recently demonstrated to be mainly mediated by electron-hole pair excitations. The present theoretical approach scrutinizes the effect of coverage by hydrogen pre-adsorbed atoms on this energy loss. Scattering can be rationalized in terms of three distinct dynamical mechanisms, the contribution of which changes with coverage. These allow, in particular, one to understand why the energy loss spectra are critically affected depending on whether scattering is analyzed in the whole space or at the specular angle.