First Analysis of the 3ν9 − ν9, 3ν9 − ν5, and 3ν9 − 2ν9 Bands of HNO3: Torsional Splitting in the ν9 Vibrational Mode

Abstract

Using Fourier transform spectra recorded at 25 and 12 μm, it has been possible to perform the first analysis of the 3ν9 − 2ν9, 3ν9 − ν5 and 3ν9 − ν9 hot bands of HNO3 located at 392.4 cm−1, 409.8 cm−1, and 830.4 cm−1, respectively. An accurate description of the torsional splitting in the v9 = 3 vibrational state was achieved, leading to the determination of the two torsional band centers Evg=3,1 = 1288.8451 cm−1 and Evg = 3,2 = 1288.9036 cm−1 and to the first determination of the ν9 torsional potential of HNO3. Finally, the 4ν9 − 3ν9, ν5 + ν9 − 2ν9, and ν5 + ν9 − ν9 hot bands were identified for the first time at 375.3-376.1 cm−1, 447.2 cm−1 and 885.424 cm−1 respectively.