The new nitrogen dioxide (NO2) linelist in the GEISA database and first identification of the ν1+2ν3-ν3 band of 14N16O2

Abstract We have generated new lists of line position, line intensity and line shape parameters of nitrogen dioxide (14N16O2 and 15N16O2), here labeled as “GEISA-19”, which have been included in the (Gestion et Etude des Informations Spectroscopiques Atmospheriques) GEISA database ( https://geisa.aeris-data.fr/ ). Except for the far infrared and the 13.3 µm regions, all spectral regions of the 1153- 4775 cm-1 spectral domain are significantly modified by this major update of the GEISA linelist. For the 6.2 µm and 3.4 µm spectral regions, which correspond to the strongest absorption of NO2, we proceed to a complete replacement of the lists for the first hot bands, ν2 + ν3-ν2 and ν1 +ν2 + ν3-ν2, respectively, and to the inclusion, whenever possible, of higher order hot bands involving the (1,0,0), (0,2,0) and (0,0,1), (1,1,0), (2,0,0) or (0,0,2) states as lower states. Also, the ν1 + ν3 linelist was improved for high rotational quantum numbers and the ν3 and ν1+ν3 bands for 15N16O2, which is the second most abundant isotopologue of NO2, are now included in the database. Finally several weak cold bands in the 2.2 to 4.9 µm region were added for the first time to the GEISA linelist. These new vibration rotation transitions were generated using existing literature data or making use of experimental data extracted from high resolution Fourier transform spectra recorded at SOLEIL for the purpose of this study. One outcome of this study was the first identification of the ν1+2ν3-ν3 hot band, leading to the first determination of the (1,0,2) energy level parameters. Also, an improved set of parameters was derived for the (0,1,1) state. The validation of the GEISA-19 linelist was performed through a detailed comparison at 296K between computed and observed Fourier transform laboratory spectra. Also, the consistency, from one band to another, of the energy levels values was carefully checked. Finally inter-comparisons and verifications were performed using the recent versions of the HITRAN ( https://hitran.org/ ) and HITEMP databases [R.J. Hargreaves, I. E. Gordon, L. S. Rothman, S. A. Tashkun, V. I. Perevalov, A. A. Lukashevskaya, S. N. Yurchenko, J. Tennyson, and H. S.P. Muller. J. Quant. Spectrosc. Radiat. Transf. 232 35 (2019)]. Our conclusions are that, at 296K, GEISA-19 is of better quality than HITRAN2016-updated or HITEMP in the overall 1153- 4775 cm-1 spectral region. As compared to its previous version, this new linelist will lead to an improved quality of the NO2 retrievals that will be performed for the future IASI-NG (Infrared Atmospheric Sounding Interferometer New Generation) satellite instrument ( https://iasi-ng.cnes.fr/fr ). However, contrary to HITEMP, GEISA-19 which does not include transitions involving high rotational quantum numbers or belonging to very high order hot bands cannot be used for hot temperature conditions.