XPS spectra of the compounds , and

Valence states of uranium in three ternary uranates KUO 3 , NaUO 3 and Ba 2 U 2 O 7 were studied using X-ray photoelectron spectroscopy (XPS). The analysis of the U4f photoelectron peak positions, peak widths at half maximum and satellite positions of U4f peaks, shows that the uranium in these compounds is present in a single valence state, namely U 5 + . Since the surface of these compounds is extremely susceptible to oxidation, the XPS spectra were measured after a carefully controlled etching of the surface using an Ar + ion beam so that the surface oxidation does not affect the XPS studies.