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Identification of Uranyl Minerals Using Oxygen K‐Edge X‐Ray Absorption Spectroscopy
Author(s) -
Ward Jesse D.,
Bowden Mark,
Resch C. Tom,
Smith Steven,
McNamara Bruce K.,
Buck Edgar C.,
Eiden Gregory C.,
Duffin Andrew M.
Publication year - 2016
Publication title -
geostandards and geoanalytical research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.037
H-Index - 73
eISSN - 1751-908X
pISSN - 1639-4488
DOI - 10.1111/j.1751-908x.2015.00337.x
Subject(s) - uranyl , uraninite , uranium , x ray absorption spectroscopy , xanes , chemistry , absorption spectroscopy , spectroscopy , absorption edge , absorption (acoustics) , silicate minerals , analytical chemistry (journal) , mineralogy , silicate , materials science , environmental chemistry , optics , metallurgy , physics , optoelectronics , quantum mechanics , organic chemistry , band gap , composite material
Although most of the world's uranium exists as pitchblende or uraninite, this mineral can be weathered to a great variety of secondary uranium minerals, most containing the uranyl cation. Anthropogenic uranium compounds can also react in the environment, leading to spatial–chemical alterations that could be useful for nuclear forensics analyses. Soft X‐ray absorption spectroscopy ( XAS ) has the advantages of being non‐destructive, element‐specific and sensitive to electronic and physical structure. The soft X‐ray probe can also be focused to a spot size on the order of tens of nanometres, providing chemical information with high spatial resolution. However, before XAS can be applied at high spatial resolution, it is necessary to find spectroscopic signatures for a variety of uranium compounds in the soft X‐ray spectral region. To that end, we collected the near edge X‐ray absorption fine structure ( NEXAFS ) spectra of a variety of common uranyl‐bearing minerals, including uranyl carbonates, oxyhydroxides, phosphates and silicates. We find that uranyl compounds can be distinguished by class (carbonate, oxyhydroxide, phosphate or silicate) based on their oxygen K‐edge absorption spectra. This work establishes a database of reference spectra for future spatially resolved analyses. We proceed to show scanning X‐ray transmission microscopy ( STXM ) data from a schoepite particle in the presence of an unknown contaminant.