Crystal-field and covalency effects in uranates: x-ray spectroscopic study


Crystal-field and covalency effects in uranates: x-ray spectroscopic study

Butorin, S.; Kvashnina, K.; Smith, A.; Popa, K.; Martin, P.

The electronic structure of U(V) and U(VI) containing uranates NaUO3 and Pb3UO6 was studied using an advanced technique, namely x-ray absorption spectroscopy (XAS) in the high-energyresolution uorescence-detection (HERFD) mode. Thanks to a significant reduction of the core-hole lifetime broadening, the crystal-field splitting of the 5f shell were probed directly in the HERFDXAS spectra collected at the U 3d edge, which is not possible with conventional XAS. In addition, the charge-transfer satellites resulting from the U 5f-O 2p hybridization were clearly resolved. The crystal-field parameters, 5f occupancy, and degree of covalency of the chemical bonding in these uranates were estimated using the Anderson impurity model by calculating the U 3d HERFD-XAS, conventional XAS, core-to-core (U 4f-to-3d transitions) resonant inelastic x-ray scattering (RIXS) and U 4f x-ray photoelectron spectra, respectively. The crystal field was found to be strong in these systems, while the 5f occupancy was determined to be 1.32 and 0.84 electrons in the ground state for NaUO3 and Pb3UO6, respectively, thus indicating a significant covalent character for these compounds.

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Publ.-Id: 23005