The average X-ray production cross sections and energies for Ar projectile K_alpha, K_beta and K REC (radiative electron capture) rays were measured for C target foils of effective thicknesses 8-450 mu g cm^-2. A model is constructed which describes these yields, the several parameters employed being fitted to the data by a chi-square fit program. The parameters involved represent the main Ar K vacancy production (a single cross section parameter, sigma _v'), the Auger and X-ray decay modes for projectiles within and after the foil, and the in-foil radiative and non-radiative electron capture (REC and NREC, respectively) decay modes. Variations in these parameters with projectile energy are estimated, and in-foil collisionally induced configuration alteration effects are considered. From the fit parameters it is possible to estimate several projectile characteristics, e.g. Ar K vacancy and K_alpha and K_beta X-ray production cross section, in-foil and post-foil average fluorescence yields and the NREC cross section. From the energy measurements the average Ar projectile configuration of an ion with a K vacancy in the thin target foil limit is estimated.