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.