Abstraction of D on Ag(1 0 0) and Ag(1 1 1) surfaces by gaseous H atoms: The role of electron–hole excitations in hot atom reactions and the transition to Eley–Rideal kinetics

H and D were adsorbed on Ag(1 0 0) and Ag(1 1 1) surfaces and characterized by thermal desorption spectroscopy. On Ag(1 0 0) surfaces hydrogen desorption from surface sites at 150 K and subsurface sites around 110 K was observed. Similarly, desorption of deuterium desorption around 150 and 110 K indicated surface and subsurface bound D. On Ag(1 1 1) surfaces only adsorption related desorption near 160 K was monitored. Abstraction of adsorbed D by gaseous H on Ag(1 0 0) is affected by reconstruction of the surface and the HD kinetics exhibits a H fluence (coverage) dependant cross-section. On Ag(1 1 1) adsorbed D is abstracted by gaseous H with a HD kinetics strictly according to the Eley–Rideal phenomenology. These features are close analogues of those observed on Cu(1 0 0) and Cu(1 1 1) surfaces. A comparison of the abstraction kinetics on various transition metals suggests that sticking of hot atoms, the reacting species on the surface, is controlled by electron–hole excitations. By this effect, the HD kinetics in abstraction on noble d-metals like Cu and Ag with a small density of states at the Fermi level and a small probability for e–h excitation exhibit Eley–Rideal phenomenology. Due to the small Ag–D bond energy on Ag(1 1 1) the attraction between incoming H and adsorbed D causes an increase of the abstraction cross-section at low D coverage, as was recently predicted by theory and verified by experiments on graphite surfaces.