Optical spectrum and crystal-field analysis of uranium trifluoride

Characterization of uranium tetrafluoride (UF4) with Raman spectroscopy

“…UF 4 and ZrF 4 were purchased from International Bio-Analytical Industries, Inc. and Stem Chemicals Inc., respectively. Both chemicals were stored within active temperature and humidity-controlled storage chambers (<10% relative humidity) to minimize contact with atmospheric water.…”

“…[9,10] Although there is some parity in the level of knowledge between these three industrially relevant uranium fluorides, UF 4 stands alone as the only one for which detailed Raman bands have neither been unambiguously characterized or modeled in silico. The Raman spectra of UF 6 , α-UF 5 and β-UF 5 solids have been well characterized, and a summation of previous efforts has been published by Armstrong et al [11] Density functional theory calculations of UF 4 to predict Raman spectral bands have likely not been performed because of the challenges of modeling relativistic unpaired electrons (U 4+ compared with U 6+ ) in current common basis sets. [12,13] This gap in UF 4 spectral properties is particularly acute as Raman spectroscopy measurements are a convenient and straightforward characterization technique for industrial processing as well as nuclear safeguards and nuclear forensic methods focused on identification of particulate species.…”

“…The Raman spectra of UF 6 , α-UF 5 and β-UF 5 solids have been well characterized, and a summation of previous efforts has been published by Armstrong et al [11] Density functional theory calculations of UF 4 to predict Raman spectral bands have likely not been performed because of the challenges of modeling relativistic unpaired electrons (U 4+ compared with U 6+ ) in current common basis sets. [12,13] This gap in UF 4 spectral properties is particularly acute as Raman spectroscopy measurements are a convenient and straightforward characterization technique for industrial processing as well as nuclear safeguards and nuclear forensic methods focused on identification of particulate species. [14][15][16] In particular, nuclear forensics represents an application where Raman analysis can provide unique probative data of chemical speciation in a timely fashion.…”

“…UF 4 is similarly important as a reaction intermediate in the fluorination process up to UF 6 and post enrichment chemical processing into uranium oxides and metal for reactor fuel fabrication. UF 5 has a minor role in the molecular laser isotope separation process as an enriched photolysis product but otherwise is largely absent from industrially relevant processes.…”

“…[2,3] Other known uranium fluorides, such as UF 3 and U 4 F 9 , are either purely of academic interest only and/or esoteric intermediate species and all with minimal published study. [4][5][6] The completeness of the chemical and structural characterization of the uranium fluorides mostly reflects their industrial application, with UF 6 by far the most completely characterized. The crystalline structure (solid phase), IR Raman spectra, 19 F NMR shifts and many other thermodynamic and kinetic properties of UF 6 are well known.…”