Isotope and surface temperature effects for hydrogen recombination on a graphite surface

We highlight the isotope and surface temperature effects for hydrogen atom recombination on a graphite surface. The reaction dynamics is studied using the semiclassical collisional method, according to which the mass and temperature effects are due to the coupling between the H/D dynamics and the dynamics of the phonon excitation/de-excitation mechanism of the substrate. All possible collisional schemes with H/D adsorbed on the surface and H/D impinging from the gas phase are considered. In particular, we focus on the recombination reaction between an H atom colliding with a D atom adsorbed on the surface and a D atom incident on an H adatom. For H2 and D2 formation, the surface temperature effect is investigated by comparing the results obtained for TS=800 K with those obtained at TS=500 K and TS=100 K. Despite the low masses involved in the dynamics, effective isotope and temperature effects were observed on the recombination probabilities, reaction energetics, and roto-vibrational states of formed molecules. The results show the need for correct treatment of the multiphonon excitation mechanism in molecule-surface interactions.