New line positions analysis of the ν1+ν2+ν3 band of NO2 at 3637.848 cm−1

Using high resolution Fourier transform spectra, a new investigation of the ν1+ν2+ν3 absorption band of nitrogen dioxide, 14N16O2, located at 3637.8479(3) cm−1 was performed. The assigned ν1+ν2+ν3 lines involve energy levels of the (1,1,1) vibrational state with rotational quantum numbers up to Ka=12 and N=54. The energy levels were satisfactorily reproduced within their experimental uncertainty using a theoretical model which takes explicitly into account the Coriolis interactions coupling the (1,1,1) levels with those of the (1,3,0) and (2,1,0) dark states, together with the spin-rotation interactions within (1,1,1) and (1,3,0) and (2,1,0). As a consequence, precise vibrational energies, rotational, spin-rotational and coupling constants were achieved for the triad {(2,1,0),(1,3,0),(1,1,1)} of interacting states of 14N16O2. Using these parameters together with the transition moment operator of the ν1+ν3 band achieved during previous studies [Mandin JY, Dana V, Perrin A, Flaud JM, Camy-Peyret C, Régalia L, Barbe A, J Mol Spectrosc 1997;181: 379-388], we have generated an improved set of line parameters (line positions and line intensities) for the ν1+ν2+ν3−ν2 hot band of 14N16O2 which absorbs together with the ν1+ν3 cold band in the 3.4 µm region.