Valence-to-core RIXS to probe uranium oxidation states

Distinguishing and quantifying the oxidation states of uranium is crucial in the actinide field. Currently, the technique of choice is HERFD XANES at the M4,5 edges. However, at U M4,5 edges the spectrum of U5+ superimposes with both U4+ and U6+ spectra, making the quantification of U5+ in compounds with mixed U4+/5+ or U5+/6+ challenging and prone to large uncertainties. Our preliminary theoretical results suggest that the valence-to-core resonant inelastic x-ray scattering (RIXS) at the U L3-edge has well separated characteristic features for U4+ and U5+ that could allow for disambiguation of the presence of U5+ and for refined quantification. With this proposal we aim at establishing if valence-to-core RIXS at the L3-edge is an adequate technique to disambiguate oxidation stats of uranium.