The 2020 release of the ExoMol database: molecular line lists for exoplanet and other hot atmospheres

TL;DR

The 2020 ExoMol database release offers extensive molecular line lists and related spectroscopic data for over 80 molecules, aiding the study of hot exoplanet atmospheres with improved accuracy and broader wavelength coverage.

Contribution

This release significantly expands the database to include 80 molecules and 190 isotopologues, integrating theoretical and laboratory data for enhanced spectroscopic analysis.

Findings

Over 700 billion transitions included

Expanded to ultraviolet wavelength data

Improved frequency accuracy for high-resolution studies

Abstract

The ExoMol database (www.exomol.com) provides molecular data for spectroscopic studies of hot atmospheres. While the data is intended for studies of exoplanets and other astronomical bodies, the dataset is widely applicable. The basic form of the database is extensive line lists; these are supplemented with partition functions, state lifetimes, cooling functions, Land\'e g-factors, temperature-dependent cross sections, opacities, pressure broadening parameters, $k$-coefficients and dipoles. This paper presents the latest release of the database which has been expanded to consider 80 molecules and 190 isotopologues totaling over 700 billion transitions. While the spectroscopic data is concentrated at infrared and visible wavelengths, ultraviolet transitions are being increasingly considered in response to requests from observers. The core of the database comes from the ExoMol project which primarily uses theoretical methods, albeit usually fine-tuned to reproduce laboratory spectra, to generate very extensive line lists for studies of hot bodies. The data has recently been supplemented by line lists deriving from direct laboratory observations, albeit usually with the use of ab initio transition intensities. A major push in the new release is towards accurate characterisation of transition frequencies for use in high resolution studies of exoplanets and other bodies.