Gerald T. Reedy

Infrared spectra and structure of some matrix‐isolated lanthanide and actinide oxides

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.

Infrared spectra of matrix‐isolated uranium oxide species. I. The stretching region

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.

Matrix-isolated FeO, NiO, and CoO: Ground-state vibrational frequencies☆

Abstract The infrared vibrational spectra of the FeO, NiO, and CoO molecules have been observed in Ar matrices at 14 K. Frequencies for each of the isotopomers 54Fe16O, 54Fe18O, 56Fe16O, 56Fe18O, 58Ni16O, 58Ni18O, 60Ni16O, 60Ni18O, 59Co16O, and 59Co18O were measured. The derived vibrational constants are: w e = 880.02 ± 1.2 and w e x e = 3.47 ± 0.6 cm −1 for 56 Fe 16 O; w e = 837.61 ± 1.1 and w e x e = 5.92 ± 0.6 cm −1 for 58 Ni 16 O; and w e = 853.75 ± 1.2 and w e x e = 3.65 ± 0.6 cm −1 for 59 Co 16 O. These results support the assignment of 5Σ+ as the ground state of FeO, 3Σ− as the ground state of NiO, and 4Σ− as the ground state of CoO.

The identification of UN in Ar matrices

Measurements of vibrational frequencies of the matrix‐isolated UN molecule are reported; leading to the identification of a linear N‐U‐N molecule. (AIP)

Infrared spectra of matrix‐isolated uranium oxide species. II. Spectral interpretation and structure of UO3

The midinfrared spectra of matrix‐isolated UO3 and its oxygen‐18 isotopes have been successfully interpreted in terms of a C2ν T‐shaped structure. Values of the two bond‐stretching and two bond‐interaction force constants determined by a normal coordinate analysis using 13 observed frequencies reproduce all peaks in the observed spectrum to within ± 0.6 cm−1. The following assignments for U16O3 species trapped in argon matrices have been obtained: ν1(A1) = 843.50, ν2(A1) = 745.65, ν4(B1) = 852.60 cm−1. The structure and intensity distribution are discussed in terms of current bonding theory for uranyl compounds.

Infrared spectra of matrix‐isolated UO+2 and NO−2

The reactions of UO and UO2 with NO and NO2 have been studied by infrared spectroscopy using the matrix isolation technique. Codeposition of vaporized UO and UO2 with NO2 and with NO gases in an argon matrix at 14 K resulted in the production of the UO+2 molecular ion paired with either a NO−2 or NO− anion. Three different reactions have been observed to yield a UO+2 cation product: (1) UO2+NO2, (2) UO2+NO, and (3) UO+NO2. Infrared absorption frequencies in the range 1150–1190 cm−1 have been measured and interpreted as the stretching modes of bent (bond angle = 109°) N16O−2, N16O18O−, and N18O−2 ions paired with UO+2. Infrared absorption frequencies in the range 770–900 cm−1 have been measured and interpreted as the stretching modes of linear U16O+2, U16O18O+, and U18O+2 paired with either NO− or NO−2.

Infrared spectra of matrix-isolated uranium oxides. III. Low-frequency modes

Infrared absorption spectra between 50 and 350 cm−1 have been obtained of argon matrices containing UO3 and UO2. The frequencies of all three expected low‐frequency vibrational modes of U16O3 have been identified and measured (±0.1 cm−1): ?3(A1)=186.2, ?5(B1)=211.6, and ?6(B2)=151.5 cm−1. The effects of 18O‐substitution have been measured and interpreted to confirm these assignments. All results are consistent with a C2v, T‐shaped structure for the UO3 molecule. The bending mode of U16O2 was measured at 225.2±0.5 cm−1. The measured frequencies of U16O18O and U18O2, the measured relative absorbances, and the observed mid‐infrared spectrum support the assignment for UO2. In addition, broad lower frequency bands were observed that may be due to impurity‐activated phonon modes of solid argon.

The infrared spectrum of matrix-isolated uranium oxide vapor species

Abstract The mid-infrared spectra of UO 2 and UO 3 formed by vaporization of UO 2± x and trapped in argon matrices have been obtained. A study of the spectra of the normal 16 O and isotopically substituted 18 O species as a function of temperature and composition of the condensed uranium oxide has led to the following assignments for the 16 O species: UO 2 (ν 3 ) = 776.1 cm −1 , UO 3 (ν 3 ) = 852.5 cm −1 , UO 3 (ν 1 ) = 745.6 cm −1 . On the basis of the isotopic data, a bond angle for UO 2 of 180 + 0 − 10° and a value of UO 2 (ν 1 ) of 765.3 cm −1 have been calculated.

Identification of matrix-isolated thorium nitride and the thorium-dinitrogen complex

The infrared stretching frequencies of Th/sup 14/N and Th/sup 15/N in solid Ar and Kr at 14 K have been measured. Multiple sites for the ThN in both matrices were observed; one site for Th/sup 14/N with anti v = 934.61 +- 0.05 cm/sup -1/ predominated after the matrix was annealed. For ThN in this site, ..omega../sub e/ = 941.9 +- 1.0 and ..omega../sub e/x/sub e/ = 3.7 +- 0.5 cm/sup -1/. No dinitride of Th was observed. A thorium-dinitrogen complex was observed with a N-N stretching frequency of 1828.59 +- 0.05 cm/sup -1/ in solid Ar. The geometry of this complex is C/sub 2v/ with equivalent nitrogen atoms and the bonding approaches that of an ion pair. 4 figures, 4 tables.

A search for the infrared fundamental of matrix‐isolated XeF

Various xenon/fluorine mixtures were photolyzed in solid argon matrices and examined in the infrared spectral region with either a Fourier transform spectrometer or with a grating spectrometer. After photolysis, a strong peak was observed at 215 cm−1 in addition to the known XeF2(ν3) peak at 549 cm−1. The appearance of the same two bands in Ar matrices containing the vapors over XeF2 indicated the assignment of the 215 cm−1 band to XeF2(ν2). The fundamental of XeF was not observed either because it is masked by the XeF2(ν2) peak or because it has a small infrared absorption coefficient.