Uranium oxides investigated by X-ray absorption and emission spectroscopies

Abstract

X-ray absorption and resonant X-ray emission measurements at the O 1s edge of the uranium oxides UO 2, U 3O 8 and UO 3 are presented. The spectral shapes of the O Kα X-ray emission spectra of UO 3 exhibit significant excitation energy dependence, from an asymmetric to a symmetric form, which differs from those of UO 2 and U 3O 8. This energy dependence is attributed to a significant difference in the oxygen–uranium hybridization between two different sites in the crystal structure of UO 3. The spectral shapes of UO 2 and U 3O 8 are also found to be different but without significant energy dependence. The experimental spectra of the valence and conduction bands of the uranium oxides are compared to the results of electronic structure calculations available in the literature.