Exoplanets, and in particular hot ones such as hot Jupiters, require a very
significant quantities of molecular spectroscopic data to model radiative
transport in their atmospheres or to interpret their spectra. This data is
commonly provided in the form of very extensive transition line lists. The size
of these line lists is such that constructing a single model may require the
consideration of several billion lines. We present a procedure to simplify this
process based on the use of cross sections. Line lists for water, H3+​, HCN
/HNC and ammonia have been turned into cross sections on a fine enough grid to
preserve their spectroscopic features. Cross sections are provided at a fixed
range of temperatures and an interpolation procedure which can be used to
generate cross sections at arbitrary temperatures is described. A web-based
interface (www.exomol.com/xsec) has been developed to allow astronomers to
download cross sections at specified temperatures and spectral resolution.
Specific examples are presented for the key water molecule.Comment: Icarus (submitted