The ν1+3ν3 absorption band of nitrogen dioxide (14N16O2) by CRDS near 6000 cm-1

The high resolution absorption spectrum of the NO2 molecule is recorded between 5855 and 6006 cm(-1) by high sensitivity cavity ring down spectroscopy (CRDS). Positions and intensities in the 5 x 10(-27) - 4 x 10(-23) cm/molecule range are derived from the profile fitting of more than 6900 lines. The absorption is dominated by the transitions of the (103)-(000) vibrational band centered at 5984.704 cm(-1). The spectrum is assigned and modeled using an effective Hamiltonian (EH) which explicitly takes into account a spin-rotational interaction and interaction of the (103) bright state with three "dark" states: (122), (080) and (410). The nu(1) +3 nu(3) band was already analyzed by Fourier transform spectroscopy (FTS) in Miljanic S., Perrin A., Orphal J., Fellows C.E., Chelin, J. Mol. Spectrosc. 2008, V. 251, P. 9-15, where resonance interactions between the (103) state and the (122) and (080) "dark" states were taken into account. More than 3000 lines are presently assigned with rotational quantum numbers N and K-a up to 59 and 13, respectively, while 1147 transitions with maximum N and K-a values of 47 and 8, respectively, were previously identified by FTS. The measured line positions are reproduced with an (obs.-calc.) rms of 0.0023 cm(-1 )by variation of 41 EH parameters. About 80 transitions reaching the (080) highly excited bending upper state and borrowing their intensity from the resonance coupling with the (103)-(000) band were assigned for the first time. The main parameter in the transition moment series of the nu(1) + 3 nu(3) band is determined from the fitting of the measured intensities. (C) 2019 Elsevier Ltd. All rights reserved.