Electronic structure and O K-edge XAS spectroscopy of U sub(3)O sub(8)

• Published in: Journal of electron spectroscopy and related phenomena 2014-06, Vol.194, p.81-87
• Main Authors: Wen, Xiao-Dong, Loble, Matthias W, Batista, Enrique R, Bauer, Eve, Boland, Kevin S, Burrell, Anthony K, Conradson, Steven D, Daly, Scott R, Kozimor, Stosh A, Minasian, Stefan G, Martin, Richard L, McCleskey, Thomas M, Scott, Brian L, Shuh, David K, Tyliszczak, Tolek
• Format: Article
• Language: eng ; fre ; ger
• Subjects: Electronic structure; Fluorescence; Orbitals; Signatures; Spectra; Uranium; Uranium oxides; X-rays
• ISSN: 0368-2048
• DOI: 10.1016/j.elspec.2014.03.005

Understanding the uranium 5f/6d orbital mixing with oxygen 2p valence orbitals in uranium oxides is important for advancing nuclear technology. Unfortunately, U-O orbital mixing is difficult to probe experimentally. In this manuscript, U-O bonding is evaluated in U sub(3)O sub(8) using O K-edge X-ray absorption spectroscopy (XAS). To confirm that the O K-edge XAS spectra were correct and did not contain contributions from surface contamination, three different sample types were investigated using three unique detection methods. Specifically an epitaxial film of U sub(3)O sub(8) deposited on Al sub(2)O sub(3) (PAD-U sub(3)O sub(8)) was probed using grazing-incidence fluorescence yield (GIFY) detection, a bulk powder of alpha -phase U sub(3)O sub(8) was analyzed with fluorescence yield (FY) detection at normal incidence, and particles of alpha -phase U sub(3)O sub(8) were studied in transmission mode using a scanning transmission X-ray microscope (STXM). Experimental spectra have been presented in the context of previously published computational results from DFT using the Heyd-Scuseria-Ernzerhof (HSE) screened hybrid functional. Overall, the comparative analyses of PAD-U sub(3)O sub(8) and alpha -phase U sub(3)O sub(8) samples enabled identification of unique signatures associated with oxygen 2p orbital mixing with both U super(V) and U super(VI) 5f and 6d valence orbitals.