Quantum effects in sticking and inelastic scattering of hydrogen and deuterium on metals, with electron-hole pair excitations

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Abstract
In this paper the first (to our knowledge) fully quantum-mechanical calculation of both the sticking coefficient and the inelastic scattering probability of atomic hydrogen and deuterium on a metal due to the electron-hole pair mechanism is presented. The results are obtained in the framework of the gettering theory of a gas in a closed vessel and by using a T-matrix formalism which includes higher-order processes. The sticking coefficient and the inelastic scattering probability are calculated with atom kinetic energy in the range 0–80 meV. In this region the inelastic scattering probability is shown to be smaller than the sticking coefficient. Within the limitations involved in our model, which only considers one electron-hole pair in the excited states, we obtain a maximum value of the sticking coefficient of hydrogen and deuterium up to about 0.8, for a reasonable parametrization of the nonadiabatic gas-surface interaction. This is related to a quantum-mechanical resonance in the transmission of the atom into the chemisorption potential, which we assume to be a square well for simplicity. The role of several step atomic transitions through unbound and bound states is analyzed for the sticking and the inelastic scattering processes.