28-30 September 2016
Tagungstätte Schloss Ringberg, Kreuth
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Contribution Invited Talk


Theoretical spectroscopy for planetary atmospheres


  • Prof. Jonathan TENNYSON

Primary authors


Fundamental molecular data play a key role for spectral characterization of astrophysical objects cool enough to form molecules in their atmospheres (cool stars, extrosolar planets and planetary discs) as well as in a broad range terrestrial applications. However, at elevated temperatures, the laboratory data for a number of key species is absent, inaccurate or incomplete. The ExoMol project aims to providing comprehensive line lists for all molecules likely to be observable in exoplanet atmospheres in the foreseeable future [1]. This is a huge undertaking which mean providing in over a hundred billion spectral lines for a large variety of molecular species [2] whose use can have a profound effect on atmospheric models [3].

The physics of molecular absorptions is complex and varies between different classes of absorbers, which are therefore divided into following topics (a) diatomic, (b) triatomics, (c) tetratomics, (d) methane and (e) larger molecules. Special techniques are being developed to treat each case. In particular, a new program Duo [4] has been developed which treats the diatomic nuclear motion problem including spin-orbit and other coupling effects directly, ie without using perturbation theory. The line lists for a number of key atmospheric species currently available from ExoMol (www.exomol.com): NH$_3$, CH$_4$, PH$_3$, H$_2$CO, AlO and HNO$_3$ , as well as PN, CaH, MgH, BeH, SiO, HCN/HNC, KCl, NaCl, NaH, ScH, SO$_2$, SO$_3$ CaO. and water. Line lists currently being constructed include those for AlH, C$_2$, C$_3$, PO, PS, PH, SH, SiH, CrH, TiH, H$_2$S, HNO$_3$, H$_3^+$, C$_2$H$_4$, CH$_3$Cl and C$_2$H$_2$. A major upgrade of the ExoMol database has just been made available [2]. This release includes new features such as pressure-broadening parameters which are important for planetary atmospheres. Examples of molecular spectra computed using the ExoMol line lists will be presented.

This ExoMol project is supported by the ERC under Advanced Investigator Project 267219.

[1] J. Tennyson and S.N. Yurchenko, MNRAS, 425, 21 (2012).

[2] J. Tennyson et al, J. Molec. Spectrosc. 327, 73 (2016).

[3] S.N. Yurchenko et al, PNAS, 111, 9379 (2014)

[4] S.N. Yurchenko, L. Lodi, J. Tennyson and A.V. Stolyarov, Comput. Phys. Comms. 202, 262 (2016).