MARVEL analysis of high-resolution rovibrational spectra of 16O12C18O

Empirical rovibrational energy levels are presented for the third most abundant, asymmetric carbon dioxide isotopologue, ¹⁶O¹²C¹⁸O, based on a compiled dataset of experimental rovibrational transitions collected from the literature. The 52 literature sources utilized provide 19,438 measured lines with unique assignments in the wavenumber range of 2–12,676 cm⁻¹. The MARVEL (Measured Active Rotational-Vibrational Energy Levels) protocol, which is built upon the theory of spectroscopic networks, validates the great majority of these transitions and outputs 8786 empirical rovibrational energy levels with an uncertainty estimation based on the experimental uncertainties of the transitions. Issues found in the literature data, such as misassignment of quantum numbers, typographical errors, and misidentifications, are fixed before including them in the final MARVEL dataset and analysis. Comparison of the empirical energy-level data of this study with those in the line lists CDSD-2019 and Ames-2021 shows good overall agreement, significantly better for CDSD-2019; some issues raised by these comparisons are discussed.