CALORIMETRIC AND XPS STUDY OF THE EFFECT OF COPPER ON THE SORPTION PROPERTIES OF DYSPROSIUM

The chemical composition of the surface of bimetallic dysprosium-coppe r films and their sorption properties towards carbon monoxide at room temperature have been studied by adsorption calorimetry and X-ray phot oelectron spectroscopy. The former method has been used to compare the behaviour of carbon monoxide and hydrogen on these films. The surface enrichment in dysprosium occurs in the bimetallic film evaporated fro m DyCu and DyCu6 Specimens. The uptake of CO is reduced by the presenc e of copper, but the adsorption heat and the rate of its production ar e little affected. C 1s spectra of the alloy surface saturated by irre versibly adsorbed CO show the existence of two distinct adsorption sta tes corresponding to dissociated and molecular species. Molecular adso rption likely occurs at dysprosium sites surrounded by copper atoms. C alorimetric measurements with hydrogen have shown that the admixture o f copper cuts down not only the uptake, but also the heat of interacti on in comparison with pure dysprosium. The results point to rapid pene tration of the dissociated H atoms into the bulk of the film and to th eir bonding to both the Dy and Cu components.