High resolution FTIR spectrum of the ν5 and 2ν9 bands of HNO3

Abstract

The Fourier transform infrared (FTIR) spectrum of the ν5 and 2ν9 bands of nitric acid (HNO3) has been measured with a resolution of 0.004 cm-1 in the frequency range of 856-910 cm-1. By fitting a total of 744 unperturbed transitions of ν5 with a standard deviation (SD) of 0.00051 cm-1, using a Watson Hamiltonian, a set of nine improved rovibrational constants for the upper state was obtained. Some transitions of 2ν9 were perturbed by a Femi resonance with the nearby ν5 state. A total of 280 unperturbed transitions of 2ν9 have been analyzed to provide nine rovibrational constants for the υ9 = 2 state with a SD of 0.00058 cm-1. The ν5 and 2ν9 bands are mainly A-type with band centres at 879.108200 ± 0.000045 and 896.44881 ± 0.00011 cm-1, respectively. A comparison of calculated line intensities of ν5 with measured values gives the transition moment as 0.155 ± 0.031 D and the integrated band intensity as 282 ± 56 cm-2 atm-1 (or 68 ± 14 km mol-1). The transition moment of the 2ν9 band is therefore estimated to be 0 17 ± 0.03 D which gives an integrated band intensity of 356 ± 71 cm-2 atm-1 (or 86 ± 17 km mol-1). © 1992.