Pressure broadening of potassium by helium and by molecular hydrogen

Absorption around the wavelengths of the resonance lines of potassium pressure broadened by helium and by molecular hydrogen is an important contributor to the opacities of late-type brown dwarfs. Satellite features appearing in the far wings of the absorption profiles are of interest as possible tests of atmospheric models. We report on experimental and theoretical studies of the first and the second resonance lines of potassium broadened by He and by molecular hydrogen.