studies, such as those performed in the Earth’s atmosphere at high resolution, Voigt profiles only provide an approximate solution to the problem [@jt584]. However Voigt profiles are in widespread use and are easily computed [@79Hum]; they are therefore used to represent pressure broadening effects in ExoMol.

The new release of ExoMol includes, where possible, pressure broadening parameters. So far, these have not been considered for vibronic spectra. HITRAN provides a source of air-broadening and self-broadening parameters [@07GoRoGa.broad] so in the absence of other sources these are taken from HITRAN 2012 [@jt557]. In gas giants H$_2$ and He are the major broadeners. There is no systematic source of parameters for these broadeners so we have to treat each system on a case-by-case basis. While some work has been performed for broadening of hot water by H$_2$ and He [@jt544; @jt636], more data would clearly be helpful in this area. Hedges and Madhusudhan [@16HeMaxx] recently put this in context by quantifying the effects of various factors involved in modelling line broadening in exoplanetary atmospheres, including completeness of broadening parameters, on molecular absorption cross sections.

ExoMol will provide Lorentzian half-widths and their temperature-exponents for key molecule-broadener systems. The availability of these parameters varies 