The nature of weak adsorption on transition metals

Abstract

Results on the adsorption of nitrogen and xenon on various crystal faces of platinum and iridium, as obtained by the field emission-probe hole technique, are reviewed in conjunction with photelectron emission data on xenon adsorption on films of various fee metals. These data are analyzed in order to discriminate between different models on the nature of weak adsorption on metals. The popular model which attributes this adsorption solely to the presence of B 5 sites is disproved. Xenon adsorption on individual crystal faces of Ir remains limited to certain sites for the atomically rough faces, but a close-packed Xe layer is formed on the smooth faces at high coverage. The nature of the adsorption bond of xenon on fee metals appears to be a combination of a chemical “charge transfer-no bond” interaction with a bonding by dispersion forces.