title: High-resolution X-ray absorption spectroscopy as a probe of crystal-field and covalency effects in actinide compounds.
abstract: Applying the high-energy resolution fluorescence-detection (HERFD) mode of X-ray absorption spectroscopy (XAS), we were able to probe, for the first time to our knowledge, the crystalline electric field (CEF) splittings of the [Formula: see text] shell directly in the HERFD-XAS spectra of actinides. Using ThO2 as an example, data measured at the Th 3d edge were interpreted within the framework of the Anderson impurity model. Because the charge-transfer satellites were also resolved in the HERFD-XAS spectra, the analysis of these satellites revealed that ThO2 is not an ionic compound as previously believed. The Th [Formula: see text] occupancy in the ground state was estimated to be twice that of the Th [Formula: see text] states. We demonstrate that HERFD-XAS allows for characterization of the CEF interaction and degree of covalency in the ground state of actinide compounds as it is extensively done for 3d transition metal systems.
authors.affiliation: Molecular and Condensed Matter Physics, Department of Physics and Astronomy, Uppsala University, 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, 38043 Grenoble, France; Institute of Resource Ecology, Helmholtz-Zentrum Dresden-Rossendorf, 01314 Dresden, Germany;
authors.forename: Kristina O
authors.initials: KO
authors.lastname: Kvashnina
authors.affiliation: Molecular and Condensed Matter Physics, Department of Physics and Astronomy, Uppsala University, SE-751 20 Uppsala, Sweden;
authors.forename: Johan R
authors.initials: JR
authors.lastname: Vegelius
authors.affiliation: Institut de Chimie Séparative de Marcoule, UMR 5257 Commissariat à l'Energie Atomique et aux Energie Alternative/CNRS/Université de Montpellier/Ecole Nationale Supérieure de Chimie de Montpellier, 30207 Bagnols-sur-Cèze, France;
authors.forename: Daniel
authors.initials: D
authors.lastname: Meyer
authors.affiliation: Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720.
authors.forename: David K
authors.initials: DK
authors.lastname: Shuh
keywords: actinide compounds; covalency; crystal field