The absorption spectrum of nitrous oxide between 7647 and 7918 cm−1

Abstract

We revisit the room temperature absorption spectrum of natural nitrous oxide recorded by high sensitivity cavity ring down spectroscopy between 7647 and 7918 cm−1 (1.31–1.26 μm) reported by Liu et al. (doi: 10.1016/j.jms.2011.03.025). In this previous analysis, 2272 transitions could be assigned in the region and no intensity information was provided. In the present work, on the basis of improved predictions of the effective operator models, the assignments could be extended to more than 3200 transitions and, more importantly, line intensities are provided for all the transitions. The assigned transitions belong to 49 bands of the 14N216O, 14N15N16O, 15N14N16O, 14N218O, and 14N217O isotopologues, 16 being newly assigned. All the identified bands correspond to the ∆P= 14 series of transitions, except for four ∆P= 12 and two ∆P= 13 bands of the 14N216O isotopologue (P= 2V1+V2+4V3 is the polyad number where Vi= 1-3 are the vibrational quantum numbers). For comparison, the HITRAN2020 database includes only the ν1+3ν3 band of the main isotopologue and a number of calculated line parameters for the fourth minor isotopologue, 14N218O. The band-by-band analysis provides accurate spectroscopic parameters of 46 bands from a fit of the measured line positions. Nine resonance perturbations were identified including a few extra lines for two 14N216O bands. The interaction mechanisms and the perturbers were assigned on the basis of the effective Hamiltonian models. The comparison with current spectroscopic databases (HITRAN, HITEMP, NOSD) is discussed. All show significant deviations compared to our observations (e.g. for ∆P= 13 band intensities). The reported results will be thus valuable to more accurately account for the absorption of nitrous oxide in the region.