The midinfrared spectra of the oxides of Ce, Pr, Sm, Eu, Tb, and Th have been obtained by vaporizing the solid oxides and trapping the vapor species in argon matrices. On the basis of oxygen-18 isotope shifts, a linear structure has been determined for PrO2, and nonlinear structures for CeO2, TbO2, and ThO2. Values of ωe and ωeχe have been determined for the monoxides of Pr, Eu, Tb, and Th from the small deviations between the observed and the theoretical harmonic isotope shifts.
Measurements of vibrational frequencies of the matrix-isolated UN molecule are reported; leading to the identification of a linear N-U-N molecule. (AIP)
Stretching modes of several uranium oxide species vaporized from tungsten and iridium Knudsen cells and deposited in argon and krypton matrices have been observed in the 700–-900 cm−1 region of the infrared. Studies of the spectra as a function of temperature and composition of the condensed urania together with normal coordinate analyses of the spectra of 16O and 18O-containing species have led to the following assignments for the 16O species in argon: U16O(ν) = 820.0 cm−1; U16O2(ν3) = 776.1 cm−1, U16O2(ν1) = 765.4 cm−1 (calc). The spectroscopic evidence strongly indicates a linear geometry for UO2. Tentative assignments for the stretching modes of UO3 are also given.
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