Isothermal measurements of the He specular reflectivity from H–Cu(111) were used to demonstrate that adsorbed H was removed from the surface in an activated process according to first-order kinetics. The measurements were taken at low coverages at 210 to 245K, where an activation-energy of 64.3kJ/mol was derived. The observation allows the ruling out of second-order molecular desorption processes and supported the conclusion that the H atoms were transported from surface to sub-surface sites by an activated process. The results confirmed an earlier suggestion that, in the low coverage limit, the sub-surface state for this system was more energetically favourable than were other states. In addition, the measurements suggested that abstraction processes took place with a probability of 4.3s0, where s0 was the initial sticking probability.

Migration and Abstraction of H-Atoms from the Cu(111) Surface. M.F.Luo, D.A.MacLaren, W.Allison: Surface Science, 2005, 586[1-3], 109-14