A (nearly) complete experimental linelist for 13C16O2, 16O13C18O, 16O13C17O, 13C18O2 and 17O13C18O by high-sensitivity CW-CRDS spectroscopy between 5851 and 7045 cm−1

An experimental database for the 13C16O2, 16O13C18O, 16O13C17O, 13C18O2 and 17O13C18O isotopologues of carbon dioxide has been constructed on the basis of the high-sensitivity absorption spectrum of carbon dioxide with 99% enrichment in 13C recorded by CW-cavity ring down spectroscopy (CW-CRDS) between 5851 and 7045 cm−1. As a result of the achieved sensitivity (typical noise equivalent absorption αmin∼2-5×10−10 cm−1) combined with the high linearity and dynamics (more than four decades) of the CW-CRDS technique, the amount of spectroscopic information contained in these spectra was considerable. A total of 8639 transitions of the 13C16O2, 16O13C18O, 16O13C17O, 13C18O2 and 17O13C18O isotopologues with line strength as low as 5×10−29 cm/molecule were assigned. They belong to a total of 150 bands, while less than 20 bands were previously reported by Fourier transform spectroscopy. The excellent agreement between the predictions of the effective operators model and the observations has allowed using an automatic search program to assign the weaker lines observed in the congested spectrum. The spectroscopic parameters of the vibrational upper levels were obtained from a fit of the measured line positions. A number of resonance interactions were observed; in particular, several occurrences of interpolyad anharmonic couplings not included in the polyad model of effective Hamiltonian, were found to affect a few bands of the 16O13C18O and 16O13C17O isotopologues. In the list of 8639 transitions, which are provided as Supplementary material, line positions are experimental values (typical uncertainty in the order of 1×10−3 cm−1), while line strengths were calculated at 296 K by using the effective operators approach (typical uncertainty in the order of 5%). In the case of the 13C16O2 isotopologue, the reported transitions represent 99.65% of the total absorbance in the region considered.