Molecular line lists:
Spectroscopic and other studies

Comprehensive description of molecular absorption and emission
for atmospheric, astrophysical and industrial applications.

Molecules of ExoMol

aiming at comprehensive production of molecular opacities important for modelling atmospheres of exoplanets and cool stars.


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

Comprehensive rotation-vibration line lists are presented for the two main isotopologues of methyl chloride, 12CH335Cl and 12CH337Cl. 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. 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, and an established 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.

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Hot line list for Methane 34to10:
A hybrid line list for CH4 and hot methane continuum

A line list for methane (CH4) is constructed as a combination of 17 million strong absorption lines relative to the reference absorption spectra and a background methane continuum in two temperature-dependent forms, of cross sections and super-lines. This approach eases the use of large high temperature line lists significantly as the computationally expensive calculation of pressure dependent profiles (e.g. Voigt) only need to be performed for a relatively small number of lines. Both the line list and cross sections were generated using a new 34 billion methane line list (34to10), which extends the 10to10 line list to higher temperatures (up to 2000 K). The new hybrid scheme can be applied to any large line lists containing billions of transitions. We recommend to use super-lines generated on a high resolution grid based on resolving power (R = 1,000,000) to model the molecular continuum as a more flexible alternative to the temperature dependent cross sections. S.N. Yurchenko, D.S. Amundsen, J. Tennyson and I. P. Waldmann, AA, 605, A95.

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ExoMol XXVII: Line list for Ethylene

Barry P. Mant, Andrey Yachmenev, Jonathan Tennyson and Sergei N. Yurchenko

A new line list for ethylene, 12C2H4 is presented. The line list is based on empirical potential energy and high level ab initio dipole moment surfaces. The line list covers the range up to 7000 cm-1 with all ro-vibrational transitions (50 billion) and thus should be applicable for temperatures up to 700~K. A cheap but reasonably technique for computing molecular opacities from vibrational band intensities is proposed and used to provide temperature dependent cross sections of ethylene for shorter wavelength and higher temperatures.

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Methane hot opacity:
Line list 10to10

is the new CH4 line list [PNAS, 111, 9379 (2014)], which contains just under 10 billion transitions. The 10to10 line list has already been demonstrated to revolutionise the accuracy of T-dwarf models and characterisa-tion of atmospheres of exoplanets and cool stars.

A hot line list for hydrogen peroxide AYTY

contains 10.3 million rotational-vibrational states and around 10 billion transition frequencies and is applicable to temperatures up to T = 1500 K.

Ahmed F. Al-Refaie et al. Mon. Not. R. Astron. Soc., 448, 1704 (2015)

Line list SAlTY

contains 16.8 billion transitions and is suitable for simulating spectra up to temperatures of 1500 K [Clara Sousa-Silva et al. Mon. Not. R. Astron. Soc., 446, 2337 (2015)]