Abstract
The Raman spectrum of uranium tetrafluoride (UF4) is unambiguously characterized with multiple Raman excitation laser sources for the first time. Across different laser excitation wavelengths, UF4 demonstrates 16 distinct Raman bands within the 50–400 cm−1 region. The observed Raman bands are representative of various F–F vibrational modes. UF4 also shows intense fluorescent bands in the 325–750 nm spectral region. Comparison of the UF4 spectrum with the ZrF4 spectrum, its crystalline analog, demonstrates a similar Raman band structure consistent with group theory predictions for expected Raman bands. Additionally, a demonstration of combined scanning electron microscopy and in situ Raman spectroscopy microanalytical measurements of UF4 particulates shows that despite the inherent weak intensity of Raman bands, identification and characterization are possible for micron‐sized particulates with modern instrumentation. The published well‐characterized UF4 spectrum is extremely relevant to nuclear materials and nuclear safeguard applications. Published 2016. This article is a U.S. Government work and is in the public domain in the USA. Journal of Raman Spectroscopy published by John Wiley & Sons Ltd.
Highlights
The uranium fluorides (UxFy) are of industrial, governmental, and academic interest; primarily dependent on their application within the nuclear fuel cycle for both uranium chemical and enrichment processes.[1]
Electron microscopy and energy dispersive spectroscopic analysis of the UF4 samples were conducted on a field emission Carl Ziess Supra 40VP Scanning Electron Microscope (SEM), and an Oxford Xmax 80 mm[2] Energy Dispersive Spectrometer (EDS) detector operated by the Oxford Inca software
Since fluorescence can affect the baseline of the Raman spectrum significantly, “bands” were identified as Raman bands as long as they were present in two or more spectra from differing laser excitation sources
Summary
The uranium fluorides (UxFy) are of industrial, governmental, and academic interest; primarily dependent on their application within the nuclear fuel cycle for both uranium chemical and enrichment processes.[1]. Microscope objective, pixel binning, grating and wavelength spectral region (fluorescence background) contributed to the integration time used during the acquisition of the Raman spectra. Micro-Raman spectra were collected on a Renishaw InVia Raman spectrometer coupled with two excitation lasers consisting of a diode source single mode λ = 785 nm, 50 mW, and Ar ion λ = 514 nm, 50 mW, lasers. Electron microscopy and energy dispersive spectroscopic analysis of the UF4 samples were conducted on a field emission Carl Ziess Supra 40VP Scanning Electron Microscope (SEM), and an Oxford Xmax 80 mm[2] Energy Dispersive Spectrometer (EDS) detector operated by the Oxford Inca software. The SCA allows in situ Raman measurements by extending excitation laser sources into the SEM and returning photon signals back to the InVia spectrometer hardware via fiber optics and a lens/mirror assembly. Raman spectra collected via the SCA were taken with both the 514 and 785 nm excitation laser sources attached to the InVia
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