Molecular adsorption on the (0001) surfaces of rare-earth metals

The adsorption of molecules on rare-earth (0001) thin films on W(110) at room temperature has been studied using photoemission spectroscopy. CO₂ adsorbs dissociatively, up to monolayer coverage, forming a carbonate species, with clean up of adventitious hydrogen also observed. Higher coverages result in molecular adsorption. H₂O and H₂S on Y(0001) also adsorb dissociatively, resulting in atomic H and S, up to monolayer coverage. Higher coverages of H₂O result in oxidation of the substrate to Y₂O₃, with formation of H₂O multilayers. H₂S dissociation appears to result in atomic S, adsorbed in both hollow and bridge sites. No indication of CH₄ adsorption was seen on Y(0001). These results, and those from the literature, are compared to data from bulk single-crystal rare-earth (0001) surfaces in an attempt to explain the origin of certain unexplained photoemission features observed on those surfaces.