keep the original computed levels as well as the uncertainties which are generally available for the empirical levels. The inclusion of approximate quantum numbers and extra energy levels included has been decided on a molecule-by-molecule basis; information on this is contained in the isotopologue definition file (see Section 5.3).

Cross sections, $k$-coefficients and pressure effects
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Many of the line lists stored in the database are huge. This makes finding other forms of storing the data desirable. ExoMol data has been used to generate temperature-dependent cross sections as a function of wavenumber [@jt542]. Such cross sections now form part of the database which will also be expanded to contain pressure-dependent cross sections and $k$-coefficient tables generated from them.

Cross sections depend on pressure, as well as temperature, due to collisional broadening by the species in the atmosphere. The provision of temperature-, pressure- and broadening species-dependent cross sections would be both computationally very demanding and again result in very large datasets. Instead we have chosen to primarily provide parameters which characterise pressure profiles for key species plus software allowing cross sections to be generated for selected temperature-pressure parameters on the user’s own computer. There is a widespread recognition that for detailed 