Highly sensitive absorption spectroscopy of carbon dioxide by ICLAS-VeCSEL between 8800 and 9530 cm−1

The absorption spectrum of carbon dioxide has been studied between 8800 and 9530 cm−1 by intracavity laser absorption spectroscopy based on a vertical external cavity surface emitting lasers (VeCSEL). Previous laboratory spectra at high resolution were nearly absent in the considered spectral region. Experiments were carried with natural carbon dioxide and with 13C enriched carbon dioxide leading to the determination of the rovibrational parameters of a total of 15 very weak vibrational transitions, including two bands of the 16O13C18O isotopologue. The observed transitions are assigned to components of the 2ν1 + 3ν3 triad and of the much weaker 5ν1 + ν3 hexad. Our measured line positions are found in excellent agreement with the predictions of the effective Hamiltonians developed for 12C16O2 and 13C16O2 but significant deviations were evidenced for the 16O13C18O minor isotopologue. The relative band intensities within each polyad are also discussed on the basis of the effective Hamiltonian model.