Crystal-Field and Covalency Effects in Uranates

An X-ray Spectroscopic Study

Journal article (2016)

Authors

Sergei M. Butorin Uppsala University
Kristina O. Kvashnina Helmholtz Zentrum Dresden Rossendorf, European Synchrotron Radiation Facility (ESRF)
A.L. Smith RST/Reactor Physics and Nuclear Materials - AS
Karin Popa European Commission Joint Research Centre, Institute for Transuranium Elements Karlsruhe
Philippe M. Martin UMR 5257 CEA/CNRS/UM/ENSCM
Research Group
RST/Reactor Physics and Nuclear Materials (AS) (TU Delft)
Copyright: © 2016 Sergei M. Butorin, Kristina O. Kvashnina, A.L. Smith, Karin Popa, Philippe M. Martin
DOI
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https://doi.org/10.1002/chem.201505091
Electronic structure X-ray absorption spectroscopy Computational chemistry Crystal-field studies Uranium
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Published Date

2016

Language

English

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Faculty

Applied Sciences

Department

RST/Radiation, Science and Technology

Research Group

RST/Reactor Physics and Nuclear Materials

Abstract

The electronic structure of UV- and UVI-containing uranates NaUO3and Pb3UO6was studied by using an advanced technique, namely X-ray absorption spectroscopy (XAS) in high-energy-resolution fluorescence-detection (HERFD) mode. Due to a significant reduction in core–hole lifetime broadening, the crystal-field splittings of the 5f shell were probed directly in HERFD-XAS spectra collected at the U 3d edge, which is not possible by using conventional XAS. In addition, the charge-transfer satellites that result from 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 by using the Anderson impurity model by calculating the U 3d HERFD-XAS, conventional XAS, core-to-core (U 4f–3d transitions) resonant inelastic X-ray scattering (RIXS), and U 4f X-ray photoelectron spectra. The crystal field was found to be strong in these systems and the 5f occupancy was determined to be 1.32 and 0.84 electrons in the ground state for NaUO3and Pb3UO6, respectively, which indicates a significant covalent character for these compounds.