First analysis of the 2ν1 + 3ν3 band of NO2 at 7192.159 cm−1

Abstract

The first investigation of the very weak 2ν1+3ν3 absorption band of nitrogen dioxide, 14N16O2, located at 7192.1587(1) cm−1 was performed using Fourier-transform incoherent broadband cavity-enhanced absorption spectroscopy (FT-IBBCEAS) in the 7080–7210cm−1 spectral range. The assigned 2ν1+3ν3 lines involve energy levels of the (203) vibrational state with rotational quantum numbers up to Ka=7 and N=47. Furthermore, due to local resonances involving energy levels from the (2,2,2)⇔(2,0,3) and (5,1,0)⇔(2,0,3) states, several transitions were also observed for the 2ν1+2ν2+2ν3 and 5ν1+ν3 dark bands, respectively. The energy levels were satisfactorily reproduced within their experimental uncertainty using a theoretical model which takes explicitly into account the Coriolis interactions between the levels of the (2,0,3) vibrational state and those of (2,2,2) and of (5,1,0). As a consequence, precise vibrational energies, rotational, and coupling constants were achieved for the triad {(5,0,1), (2,2,2), (2,0,3)} of interacting states of 14N16O2. This theoretical model also accounts for the electron spin-rotation resonances within the (2,0,3), (2,2,2) and (5,1,0) vibrational states. However, owing to the limited experimental resolution (∼0.075cm−1), it was not possible to observe the spin-rotation doublet structure. As a consequence, the spin-rotation constants in the {(2,2,2), (2,0,3), (5,1,0)} excited states were maintained fixed to their ground state values in this study. Using these parameters a comprehensive list of line positions and line intensities was generated for the 2ν1+3ν3 band of NO2.