Uranium complexes are of considerable interest both in fundamental actinide chemistry and in nuclear technologies from uranium nuclear fuels to chemical separation processes. We studied the electronic structure and chemical bonding of UO₂Cl₄^2-, UCl₆^1-, and UCl₆^2- using recent advances in X-ray spectroscopy experiments and in multiconfigurational ab initio calculations. X-ray absorption (XAS) and emission spectroscopy provide element-specific probes, giving insight into the oxidation state and ligand environment around a specific absorbing atom. In this presentation we will show the results of applying U M-edge (3d→5f) XAS and valence-to-core (VTC) M₄-edge (3d_3/2 →5f_5/2 absorption then 5f_5/2 → 3d_3/2 emission) resonant inelastic X-ray scattering (RIXS) to probe the valence excitations involving 5f orbitals. The VTC M₄-edge RIXS significantly reduces the linewidth broadening in M₄-edge XAS, thus allows detailed and unbiased assignment of the observed spectral features by multireference wavefunction-based calculations. These findings have great potential to benchmark and inspire further exploration on electronic structures of actinide elements by utilizing RIXS technique both in theoretical and experimental interpretation.

Joseph Kasper

Appearances