Absorption spectrum of nitrous acid for the ν1+2 ν3 band studied with continuous-wave cavity ring-down spectroscopy and theoretical calculations

Abstract

We present the high resolution absorption measurements of gaseous HONO at room temperature using continuous-wave cavity ring-down spectroscopy in the near-infrared region between 6017 and 6067 cm −1 at a resolution of 1 pm (0.037 cm −1). For the trans-HONO isomer an extensive analysis of the ν 1+2 ν 3 combination band 6045.8089 cm –1 was performed starting from the results of a previous study for the 1 1 and 3 1 vibrational states [Guilmot J-M, Godefroid M, Herman M. Rovibrational parameters for trans-nitrous acid. J Mol Spectrosc 1993;160:387–400]. The present combination band is perturbed because of the existence of several dark states of HONO which could not be identified unambiguously. The rotational constants achieved for the 1 13 2 state deviate slightly from the values which are predicted from the rotational constants achieved in the previous studies for the 1 1 and 3 1 vibrational states of trans-HONO.