Crystal‐Field and Covalency Effects in Uranates: An X‐ray Spectroscopic Study. Issue 28 (3rd June 2016)

• Record Type: Journal Article
• Authors: Butorin, Sergei M.; Kvashnina, Kristina O.; Smith, Anna L.; Popa, Karin; Martin, Philippe M.
• Is Part Of: Chemistry. Volume 22:Issue 28(2016)
• Page Start: 9693
• Page End: 9698
• Publication Date: 2016-06-03
• Subjects: computational chemistry -- crystal-field studies -- electronic structure -- uranium -- X-ray absorption spectroscopy; Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201505091
• Languages: English
• ISSNs: 0947-6539

Abstract

Abstract: The electronic structure of U V ‐ and U VI ‐containing uranates NaUO3 and Pb3 UO6 was 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 NaUO3 and Pb3 UO6, respectively, which indicates a significant covalent character for these compounds. Abstract : Now U see it : The electronic structure of U V ‐ and U VI ‐containing uranates was studied by using X‐ray absorption spectroscopy (XAS) in the high‐energy‐resolution fluorescence‐detection (HERFD) mode (see figure). A significant reduction in the core–hole lifetime broadening allowed the crystal‐field splittings of the 5f shell to be probed directly in HERFD‐XAS spectra collected at the U 3d edge. Charge‐transfer satellites due to U 5f–O 2p hybridization were clearly resolved.