An ab Initio Study of Vibrational Spectra of Nitrous Acid Isomers

The geometries and fundamental vibrational frequencies of trans-and C-2v- nitrous acid have been determined by ab initio calculations at the MP2 level with 6-31G** and 6-311+G** basis sets. The calculation results satisfactorily reproduce the experimental structural and vibrational spectral features of trans-HONO. Calculations at the same levels indicate that the C-2v-HNO2 is also a stable conformer of nitrous acid. The calculated frequencies of C-2v-HNO2 are in good agreement with the matrix infrared spectral features.