ExoMol line lists – LVIII. High-temperature molecular line list of carbonyl sulphide (OCS)

Abstract

A new molecular line list covering wavelengths λ > 1 μm (the 0 – 10 000 cm−1 range) for the main isotopologue of carbonyl sulphide 16O12C32S is presented. The OCS line list, named OYT8, contains almost 2.5 billion transitions between 2.4 million rotation-vibration energy levels with the total angular momentum up to J = 223. It is suitable for high-temperature environments up to T = 2000 K. Line list calculations were performed with the variational nuclear motion code trove in conjunction with a highly accurate, empirically-refined potential energy surface and a newly computed ab initio dipole moment surface of OCS. The OYT8 line list is adapted for high-resolution applications by replacing computed energy levels with empirically-derived values of OCS where available. Comparisons of the OYT8 line list with other OCS line lists and spectra yields excellent agreement for both strong and weak spectroscopic bands. The increased coverage of the OYT8 line list and the many new spectral features that are available will greatly facilitate the future observation of OCS on exoplanets. Carbonyl sulphide joins a growing number of sulphur-bearing molecules available from the ExoMol database. The OYT8 line list along with the associated temperature- and pressure-dependent molecular opacities can be downloaded from www.exomol.com and the CDS astronomical database.

A highly accurate potential energy surface for carbonyl sulphide (OCS): how important are the ab initio calculations?

“…Exoplanets can possess temperatures ranging into the thousands of Kelvin but only room-temperature OCS line list data with incomplete coverage is available from the HITRAN spectroscopic database. 83 A comprehensive molecular line list of OCS, based on the CBS-HL ref PES, has recently been computed 84 for the ExoMol database, 53–55 which is providing extensive high-temperature spectroscopic data for exoplanets.…”