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Title: Theoretical modeling of the uranium 4f XPS for U(VI) and U(IV) oxides

X-ray photoelectron spectroscopy (XPS), and in particular the U4f level, has been widely used to elucidate the chemical state of uranium in various materials. In large part, previous experimental work has relied on comparing the U4f spectra of an unknown to some “standard” or using qualitative intuitive judgments on the expected behavior of the primary lines and satellite structures as a function of oxidation state and bonding environment. Such approaches are useful and can be sufficiently robust to make defensible claims. Nonetheless, there is no quantitative understanding of the chemistry and physics that control satellite structures or even the shape of the primary peaks. To address this issue, we used a rigorous, strictly ab initio theoretical approach to investigate the U(4f) XPS of U oxides with formal U(VI) and U(IV) oxidation states. Our theoretical studies are based on the electronic structures of embedded cluster models, where bonding between U and O is explicitly incorporated. We demonstrate that treatment of the many-body character of the cluster wavefunctions is essential to correctly model and interpret the U4f XPS. Here we definitively show that shake configurations, where an electron is transferred from a dominantly O2p bonding orbital into dominantly 5f or 6d antibondingmore » orbitals, are indeed responsible for the major satellite features. Based on this rigorous theoretical framework, it is possible to establish quantitative relationships between features of the XPS spectra and the chemistry of the material.« less
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Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics, 139(24):244704
Research Org:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US)
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Country of Publication:
United States
XPS, satellites, U4f, theory