A study of the hydrolysis of uranium hexafluoride by Fourier transform infrared spectroscopy

The reaction of uranium hexafluride with water has been studied by using Fourier transform infrared (FT-IR) spectroscopy. Several different methods for accomplishing this task have been carried out. In addition, interpretations of the results have been made. These interpretations have been based on literature values for the reactants and for compounds analogous to possible products.

It was shown that classical matrix-isolation techniques proved to be unsatisfactory for studying this reaction. Other methods were developed in order to obtain results. They were: (1) the codeposition of pure UF₆ and H₂O on a cold window at 16°K, (2) the codeposition of argon matrix to sample ratios of 10:1 to 2:1 of UF₆ and H₂O at 16°K, and (3) the annealing of the samples produced by (1) and (2) while they were being scanned with FT-IR.

Other methods which were tried and found to be non-productive are also presented. Also, an experiment in which an attempt to volatilize UOF₄ in vacuo is presented. This volatilization was attempted in a cryostat at 16°K with the hope of isolating UF₄ in a matrix on a cold window.

FT-IR spectra obtained in these experiments are presented and discussed. The results obtained are: (1) UF₆ and H₂O show no propensity to react at cryogenic temperatures because of thermodynamic factors, (2) they do react at temperatures above 150°K, (3) there is a concentration factor that influences their reaction, (4) their reaction seems to be relatively complex and the reaction pathway involves several comparatively stable species, (5) these species are evidenced by possible U-F, UO₂, U-O and other IR bands, and (6) the attempted volatilization of UOF₄ supports prior indications that the molecule undergoes disproportionation into UF₆ and other products when heated. Finally, possibilities of extending these experiments are discussed.