title: Characteristics of chemical bonding of pentavalent uranium in La-doped UO2.
abstract: The effect of La doping on the electronic structure of U in UO2was studied using an advanced technique, namely, X-ray absorption spectroscopy (XAS) in the high-energy-resolution fluorescence-detection (HERFD) mode, at the U 3d3/2(M4) edge. Thanks to a significant reduction of the core-hole lifetime broadening and distinct chemical shifts of the HERFD-XAS lines, the U(v) formation as a result of La doping was identified. The isolated contribution of U(v) in the M4HERFD-XAS spectrum reveals the so-called charge-transfer satellites due to the U 5f-O 2p hybridization. The analysis of the experimental data within the framework of the Anderson impurity model (AIM) indicates a significant change in the characteristics and degree of covalency for the chemical bonding in the U(v) subsystem of UO2as compared to undoped UO2, which is a Mott-Hubbard system. The results are also supported by AIM calculations of X-ray photoelectron and optical absorption data.
authors.affiliation: Molecular and Condensed Matter Physics, Department of Physics and Astronomy, Uppsala University, P.O. Box 516, SE-751 20 Uppsala, Sweden. sergei.butorin@physics.uu.se.
authors.forename: Sergei M
authors.initials: SM
authors.lastname: Butorin
authors.affiliation: The European Synchrotron, CS40220, 38043 Grenoble Cedex 9, France and Helmholtz Zentrum Dresden-Rossendorf (HZDR), Institute of Resource Ecology, P.O. Box 510119, 01314, Dresden, Germany.
authors.forename: Kristina O
authors.initials: KO
authors.lastname: Kvashnina
authors.affiliation: European Commission, Joint Research Centre, Institute for Transuranium Elements, P.O. Box 2340, D-76125 Karlsruhe, Germany.
authors.forename: Damien
authors.initials: D
authors.lastname: Prieur
authors.affiliation: Université Lille, CNRS, Centrale Lille, ENSCL, Université Artois, UMR 8181, UCCS, Unité de Catalyse et Chimie du Solide, F-59000 Lille, France.
authors.forename: Murielle
authors.initials: M
authors.lastname: Rivenet
authors.affiliation: CEA Marcoule, CEA, DEN, DTEC/SECA/LCC, F-30207 Bagnols-sur-Cèze Cedex, France.
authors.forename: Philippe M
authors.initials: PM
authors.lastname: Martin