  The Kennard-Stepanov relation describes a thermodynamic, Boltzmann-type
scaling between the absorption and emission spectral profiles of an absorber,
which applies in many liquid state dye solutions as well as in semiconductor
systems. Here we examine absorption and emission spectra of rubidium atoms in
dense argon buffer gas environment. We demonstrate that the Kennard-Stepanov
relation between absorption and emission spectra is well fulfilled in the
collisionally broadened atomic gas system. Our experimental findings are
supported by a simple theoretical model.
