Local Symmetry Effects in Actinide 4f X-ray Absorption in Oxides
2016 (English)In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 88, no 8, 4169-4173 p.Article in journal (Refereed) PublishedText
A systematic X-ray absorption study at actinide N-6,(7) (4f -> 6d transitions) edges was performed for light-actinide oxides including data obtained for the first time for NpO2, PuO2 and UO3. The measurements were supported by ab initio calculations based on local-density approximation. with added 5f-5f Coulomb interaction (LDA+U). Improved energy resolution compared to common experiments at actinide L-2,L-3 (2p -> 6d transitions) edges allowed us to resolve the major structures of the 13 unoccupied 6d density of states (DOS) and estimate the crystal-field 116) splittings in the 6d shell directly from the spectra of light-actinide dioxides. The measurements demonstrated an enhanced sensitivity of the N-6,N-7, spectral shape to changes in the compound crystal structure. For nonstoichiometric NpO2-x, the filling of the entire band gap with Np 6d states was observed thus supporting a phase coexistence of Np metal and stoichiometric NpO2 which is in agreement with the tentative Np-O phase diagram.
Place, publisher, year, edition, pages
2016. Vol. 88, no 8, 4169-4173 p.
IdentifiersURN: urn:nbn:se:uu:diva-297906DOI: 10.1021/acs.analchem.5b04380ISI: 000374706000001PubMedID: 27008406OAI: oai:DiVA.org:uu-297906DiVA: diva2:944302
FunderSwedish Research CouncilEU, FP7, Seventh Framework Programme, 269903Swedish National Infrastructure for Computing (SNIC)