Micro-Raman Spectrum of Triuranium Octoxide, U ₃ O ₈

Uranium oxides are important nuclear reactor fuels and there are at least nine oxides known, many of which are mixed valence and polymorphic. Transmission-IR spectroscopy has proven to be a useful method for characterizing the oxides. For instance, IR spectra and vibrational assignments have been reported for UO2, UO2.05, UO2.08, UO2.18, U4O9, and U3O8. Some of the results have recently been verified for UO2 and U3O8 with the use of a metal light pipe technique. Previous attempts to obtain complementary Raman data were frustrated because of the extremely dark colors of the materials. We have now shown that it is possible to surmount this problem using micro-Raman spectroscopy, and we have reported characteristic Raman spectra of UO2, U4O9, U3O7, and U3O8. However, no assignments were proposed for the observed spectra.