Study of H+NO2 in an Argon Matrix between 4 and 14°K; The Infrared Spectra of Matrix-Isolated cis- and trans-HONO

The matrix-isolated infrared spectra of cis- and trans-nitrous acid molecules have been obtained in argon at low temperatures by the reaction of H atoms with NO2. The spectra, which include 15N- and 18O-substituted molecules, are not complicated by the stabilization of the acid in the presence of large concentrations of NO, NO2, and H2O. All six fundamentals of the cis and three of the trans isomers have been identified, and found generally to confirm the assignments of a previous study where some uncertainty did exist. The normal coordinate calculation performed for the cis molecule predicted the average frequencies of the four 15N- and 18O-substituted species with an error of 0.60 cm−1 or 0.068%.