X‐ray photoelectron spectra of the U 4f levels in UF4, UF5 and UF6

Trowbridge, L.D.; Richards, H.L.

doi:10.1002/sia.740040303

Cited by 12 publications

(3 citation statements)

References 5 publications

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“…Data on U(VI) halides is limited to UF 6 . As expected the BE is significantly higher than for the UO 3 polymorphs, with reported BEs for U4f 7/2 at 384.3–384.9 eV after referencing to F1s at 684.6 eV . Thibaut et al .…”

Section: U4f7/2 Binding Energysupporting

confidence: 64%

XPS determination of uranium oxidation states

Ilton

Bagus

2011

Surface & Interface Analysis

210

118

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This contribution is both a review of different aspects of X-ray photoelectron spectroscopy that can help one determine U oxidation states and a personal perspective on how to effectively model the X-ray photoelectron spectroscopy of complicated mixed-valence U phases. After a discussion of the valence band, the focus lingers on the U4f region, where the use of binding energies, satellite structures, and peak shapes is discussed in some detail. Binding energies were shown to be very dependent on composition/structure and consequently unreliable guides to oxidation state, particularly where assignment of composition is difficult. Likewise, the spin orbit split 4f 7/2 and 4f 5/2 peak shapes do not carry significant information on oxidation states. In contrast, both satellite-primary peak binding energy separations, as well as intensities to a lesser extent, are relatively insensitive to composition/structure within the oxide-hydroxide-hydrate system and can be used to both identify and help quantify U oxidation states in mixed valence phases. An example of the usefulness of the satellite structure in constraining the interpretation of a complex multivalence U compound is given. Copyright © 2011 John Wiley & Sons, Ltd.Keywords: XPS; uranium; oxidation states IntroductionOne of the great strengths of X-ray photoelectron spectroscopy ( XPS) is its ability to elucidate the valence state of a wide range of elements at the near-surface of materials. Although many features of interest concern bulk properties, it is the surface and the near-surface that has immediate contact with its surroundings and consequently mediates most reactions. With the renewed interest in nuclear energy, characterizing the surface composition and chemical state of actinide-containing materials is important for both industrial applications and understanding the fate and transport of actinides in the environment. This perspective article is focused on uranium as the data set is by far the most comprehensive of all the actinides where an appreciable literature on the XPS of U compounds dates back to the beginnings of the commercialization of XPS in the 1970s. For an early paper on the XPS of a broad range of actinide oxides we refer the reader to Veal et al.[1] A basic understanding of XPS principles is assumed throughout and will not be reviewed.On one level, determining oxidation states with XPS would appear to be a simple exercise of comparing the binding energies (BEs) of core levels to well characterized standards; so why bother? However, interpreting the oxidation states of samples with mixed valence, unknown structures, and complicated or different compositions can pose a challenge, as with any analytical technique. In fact, composition can strongly affect uranium core-level BEs and potentially confuse the determination of oxidation states. For example, perhaps one is working in an oxidizing system and only expects U(VI), yet the U4f 7/2 line has a peak at 382.0 eV and a shoulder at 380.5 eV. Does the shoulder represent a reduced species, po...

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Section: U4f7/2 Binding Energysupporting

confidence: 64%

XPS determination of uranium oxidation states

Ilton

Bagus

2011

Surface & Interface Analysis

210

118

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“…In general, the valence state for actinide‐based systems are between An 3+ and An 4+ due to the lower spin density [44] . In contrast to the U 5+ state in UF 5 and U 2 O 5 , [53] U ions have the mixed‐valence state in U 2 N 3 . 5 f 2.23 atomic configuration suggests the valence state of U 3.77+ for U ions in U 2 N 3 if N ions are assumed to be trivalent, [8,54] given that the high‐lying 7 s and 6 d orbitals being more readily contributing into the chemical bonding as compared to 5 f orbitals [45] …”

Section: Resultsmentioning

confidence: 99%

Valence Fluctuation of Uranium Ions in Uranium Sesquinitride Revealed by Dynamical Mean‐field Theory Merged with Density Functional Theory

Cao

et al. 2023

ChemPhysChem

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The electronic properties, in particular, the occupation number of 5f electrons and the valence state of U ions in uranium sesquinitride (U2N3) are studied by using density functional theory (DFT) calculations merged with dynamical mean‐field theory (DMFT). The results demonstrate that j=5/2 and j=7/2 manifolds are in the weakly correlated metallic and weakly correlated insulating regimes, respectively. The quasi‐particle weights indicate that LS coupling scheme is more feasible for 5f electrons, which are not in the orbital‐selective localized state. The weighted summation of the occupation probabilities of 5fn (n=0,1,2,3,4) atomic configurations suggests that 5f electrons have the inter‐configuration fluctuation, or the mixed‐valence state for U ions, together with an average occupation number of 5f electrons n5f∼2.234, which is in good agreement with the electron localization function (ELF) and occupation analysis based on other DFT‐based calculations. The 5fn‐mixing‐driven inter‐configuration fluctuation might originate from the dual nature of 5f electrons, and the flexible electronic configuration of U ions. Finally, the so‐called quasiparticle band structure is also discussed.

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“…These peaks are observed in the higher energy region compared with those corresponding to the oxide compounds of U(IV) and U(VI) [35,36], and located in the further higher energy region compared with those observed in the deposits obtained from NaF solution. This suggests that the ratio of F À ions interacted with uranium is larger than that in the NaF solution system, because it has been known that the peaks corresponding to U 4f 7/2 shift to higher energy with an increase in the ratio of F component composing U(VI) compounds [37]. Such an increase in F component in the present system seems to be explained by the facts that the F À concentration (0.19 M) of BMICl solution soaked the steel wastes is higher than that (0.15 M) in the spent NaF system.…”

Section: Potential Controlled Electrolysis Of Solutions Obtained In Dmentioning

confidence: 93%