Ab initio calculation of the non-relativistic free-free Gaunt factor incorporating plasma screening

We present calculations of Gaunt factors for free-free absorption over a wide range of temperatures and densities. The calculations employ a partial wave expansion approach, which is able to account for plasma screening within the calculation of the free-free Gaunt factor. Much of the existing Gaunt factor data pertains to hydrogenic systems, and plasma screening is often incorporated in opacity calculations using approximate methods. The use of a more accurate method allows us to determine the accuracy of such approximations in calculations of the free-free monochromatic and mean opacities.