High sensitivity CW-CRDS spectroscopy of 12C 16O 2, 16O 12C 17O and 16O 12C 18O between 5851 and 7045 cm −1: Line positions analysis and critical review of the current databases

Abstract

The exhaustive line positions analysis of the absorption spectrum of carbon dioxide in natural abundance has been performed on the basis of high sensitivity CW-Cavity Ring Down spectroscopy between 5851 and 7045 cm −1 (1.71–1.42 μm). The achieved sensitivity (noise equivalent absorption α min ∼ 2–5 × 10 −10 cm −1) have allowed the detection of 8293 transitions of the 12C 16O 2, 16O 12C 17O and 16O 12C 18O isotopologues. They belong to a total of 130 bands. Line intensities of the weakest transitions are on the order of 2 × 10 −29 cm/molecule. The rovibrational assignments were performed on the basis of accurate predictions of the effective Hamiltonian model of the respective isotopologues. The band-by-band analysis has allowed deriving accurate spectroscopic parameters of 121 bands from a fit of the measured line positions. A number of resonance interactions were identified. In particular, the first observation of an interpolyad coupling is reported for the 16O 12C 18O isotopologue. The results of the complete line positions analysis are provided as Supplementary material. The obtained experimental dataset which is the most complete in the considered region, has been used for a critical review of the most currently used spectroscopic databases of carbon dioxide: HITRAN, GEISA, HITEMP, and the recent JPL and CDSD databases.