The vibrational spectra of four isotopic nitric acid molecules including the 15N and D species have been obtained in the vapor and solid phases. The Raman spectra of anhydrous and wet normal nitric acid were also studied. Previous assignment of the fundamental modes has been revised, and the spectra in the three phases have been correlated. The potential barrier against internal rotation of the hydroxyl group has been calculated to be 7.8±0.1 kcal/mole in both the H and D acids. A set of least-squares fitted valence force constants which reproduce the observed fundamentals with an average error of 0.6% has been derived.
Pressed alkali halide disks of infrared spectroscopy have been used as matrices to trap and to stabilize the carbon dioxide anion free radical. The radical was generated by exposing disks containing the formate ion in solid solution to gamma rays from a cobalt source. The ESR, the ultraviolet, and the infrared spectra of the radical have been identified. From the carbon−12 and −13 isotopic frequencies of the antisymmetric CO-bond stretching infrared band, a valence angle of 127°±8° was calculated for this radical. The radical reacted with water to produce bicarbonate and formate ions.
The temperature dependence of the infrared spectra of N2O4 and N2O3 in the solid phase at liquid-nitrogen temperatures has been investigated. From these spectra of both 14N and 15N isotopic molecules, absorption bands which may be assigned to unstable isomers of these nitrogen oxides have been identified. A reasonable interpretation of these absorption bands can be made by assuming the existence of two unstable forms of N2O4 and one of N2O3.
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