ExoMol line lists - XXIX. The rotation-vibration spectrum of methyl chloride up to 1200 K

TL;DR

This paper provides extensive rotation-vibration line lists for methyl chloride isotopologues, suitable for high-temperature conditions up to 1200 K, enabling improved spectral modeling for atmospheric and astrophysical research.

Contribution

It introduces new, comprehensive line lists for methyl chloride up to 1200 K, with over 166 billion transitions, refined using experimental data and ab initio calculations.

Findings

Line lists agree well with experimental spectra

Accurate modeling of methyl chloride absorption at high temperatures

Extensive data for astrophysical and atmospheric applications

Abstract

Comprehensive rotation-vibration line lists are presented for the two main isotopologues of methyl chloride, $^{12}$CH$_3{}^{35}$Cl and $^{12}$CH$_3{}^{37}$Cl. The line lists, OYT-35 and OYT-37, are suitable for temperatures up to $T=1200\,$K and consider transitions with rotational excitation up to $J=85$ in the wavenumber range $0$--$6400\,$cm$^{-1}$ (wavelengths $\lambda> 1.56\,\mu$m). Over 166 billion transitions between 10.2 million energy levels have been calculated variationally for each line list using a new empirically refined potential energy surface, determined by refining to 739 experimentally derived energy levels up to $J=5$, and an established {\it ab initio} dipole moment surface. The OYT line lists show excellent agreement with newly measured high-temperature infrared absorption cross-sections, reproducing both strong and weak intensity features across the spectrum. The line lists are available from the ExoMol database and the CDS database.