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Proceedings Paper

Fixed-angle reflectance from uranium compounds and U-bearing minerals: experimental challenges to determine the optical constants n and k
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Paper Abstract

Fixed-angle reflectance spectroscopy using a commercial Fourier transform infrared (FTIR) spectrometer was employed to derive the optical constants n and k of several uranium compounds. This technique relies upon measurement of the quantitative reflectance R(ν) spectra from a polished surface across a broad spectral range (in this case, the mid- and far-IR covering ca. 7500 to 50 cm-1 ) followed by application of the Kramers-Kronig transformation (KKT). Near-normal fixed-angle measurements as used in this technique require continuous reflectance spectra to as low a wavenumber value as possible. Here, we discuss some of the many challenges in measuring the far-IR and very far-IR (terahertz) spectra using an interferometric instrument, particularly those stemming from small sample sizes, typically just millimeters on a face for crystalline samples, as well as limitations due to optical components and diffraction. We apply this method to single-crystal UO2 and its mineralogical form uraninite, as well as other Ubearing minerals such as autunite [Ca(UO2)2(PO4)2·8-12H2O] and the dehydrated form of autunite, meta-autunite. In addition to the specular reflectance spectra, x-ray diffractometry was used as a confirmatory technique to analyze the surface composition of the species. Deriving the infrared optical constants for such U-bearing species (as well as other solids) will enable nondestructive detection under a variety of environmental and compositional conditions.

Paper Details

Date Published: 17 May 2019
PDF: 8 pages
Proc. SPIE 11010, Chemical, Biological, Radiological, Nuclear, and Explosives (CBRNE) Sensing XX, 110100S (17 May 2019); doi: 10.1117/12.2519504
Show Author Affiliations
Brent M. DeVetter, Pacific Northwest National Lab. (United States)
C. Tom Resch, Pacific Northwest National Lab. (United States)
Tanya L. Myers, Pacific Northwest National Lab. (United States)
Jordan F. Corbey, Pacific Northwest National Lab. (United States)
Molly Rose K. Kelly-Gorham, Pacific Northwest National Lab. (United States)
Bret D. Cannon, Pacific Northwest National Lab. (United States)
Nicole K. Scharko, Pacific Northwest National Lab. (United States)
Timothy J. Johnson, Pacific Northwest National Lab. (United States)


Published in SPIE Proceedings Vol. 11010:
Chemical, Biological, Radiological, Nuclear, and Explosives (CBRNE) Sensing XX
Jason A. Guicheteau; Chris R. Howle, Editor(s)

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