Pressure-dependent water absorption cross sections for exoplanets and other atmospheres

Many atmospheres (cool stars, brown dwarfs, giant planets, extrasolar planets) are predominately composed of molecular hydrogen and helium.

H216O is one of the best measured molecules in extrasolar planetary atmospheres to date and a major compound in the atmospheres of brown-dwarfs and oxygen-rich cool stars, yet the scope of experimental and theoretical studies on the pressure broadening of water vapour lines by collision with hydrogen and helium remains limited.

Theoretical H2- and He-broadening parameters of water vapour lines (rotational quantum number J up to 50) are obtained for temperatures in the range 300 - 2000 K. Two approaches for calculation of line widths were used: (i) the averaged energy difference method and (ii) the empirical expression for J\p J\pp-dependence.

Voigt profiles based on these widths and the BT2 line list are used to generate high resolution (Δν~ = 0.01 \cm) pressure broadened cross sections for a fixed range of temperatures and pressures between 300 - 2000 K and 0.001 - 10 bar. An interpolation procedure which can be used to determine cross sections at intermediate temperature and pressure is described. Pressure broadening parameters and cross sections are presented in new ExoMol format.

Emma J. Barton, C. Hill, Sergei N. Yurchenko, Jonathan Tennyson, Anna S. Dudaryonok, Nina N. Lavrentieva
(Submitted on 27 Oct 2016)

Comments: 40 pages, 5 Figures, 6 Tables JQSRT, in press
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Atmospheric and Oceanic Physics (
Cite as: arXiv:1610.09008 [astro-ph.EP] (or arXiv:1610.09008v1 [astro-ph.EP] for this version)
Submission history
From: Jonathan Tennyson
[v1] Thu, 27 Oct 2016 20:42:40 GMT (4491kb,D)

Please follow Astrobiology on Twitter.

  • submit to reddit