We present vacuum ultraviolet absorption spectra and an asymmetric line shape simulation of the 6s and 6s' Rydberg states ( including the blue satellite bands) of xenon doped into argon, from low argon number density to the density of the triple point liquid, at both non-critical temperatures and near (+0.5 degrees C) the critical isotherm of argon (i.e., -122.3 degrees C). The argon-induced shift in the simulated primary transition of the Xe 6s and 6s' Rydberg states is presented as a function of argon number density for non-critical temperatures and along an isotherm near the critical temperature. This shift demonstrates a perturber critical point effect on the transition energies of low-n dopant Rydberg states. (C) 2008 Elsevier B.V. All rights reserved.