At elevated temperatures the spectra of polyatomic molecules become extremely complicated with millions, or even billions, of transitions potentially playing an important role. The atmospheres of cool stars and "hot Jupiter" extrasolar planets are rich with molecules in the temperature range 1000 to 3000 K and their properties are strongly influenced by the infrared and visible spectra of these molecules. Key parameters for establishing exoplanet properties and formation history are the carbon abundance and the carbon/oxygen ratio. Establishing these observationally requires extensive, reliable lists of spectral lines for a number species. The ExoMol project (www.exomol.com) aims to construct line lists of molecular transitions suitable for spectroscopic and atmospheric modelling of cool stars and exoplanets [1]. As huge numbers of lines are required, the line lists are computed on the basis of a thorough quantum mechanical treatment of the problem and tested against available laboratory data, rather than constructed experimentally. Line lists already exist for some stable diatomics, water and ammonia. A revised line list for the HCN/HNC system has been provided [2]. However, line lists are still required for many carbon-bearing species. Recently we constructed a 10 billion line list of methane transitions [2], which has been shown to resolve problems with modeling methane at high temperatures [3]. Progress on line lists for other carbon-containing species such as C3, HCCH and higher hydrocarbons will be reported at the meeting. [1] J. Tennyson and S.N. Yurchenko, Mon. Not. Roy. astr. Soc. 425, 21 (2012). [2] R.J. Barber, J. Strange, C. Hill, O.L. Polyansky, G. Mellau, S.N. Yurchenko and J. Tennyson, Mon. Not. R. astr. Soc., 437, 1828 (2014) [2] S.N. Yurchenko, J. Tennyson, Mon. Not. R. astr. Soc.}, {\bf 440}, 1649-1661 (2014). [3] S.N. Yurchenko, J. Tennyson, M.D.J. Hollis and G.Tinetti, Proc. Nat. Acad. Sci., 11, 9379 (2014).

Molecular line lists of carbon-containing molecules for exoplanets and other hot bodies

249th National Meeting (2015)

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