The observation of isotope shifts due to a difference in mass number by diode laser absorption spectroscopy (DLAS) is a powerful approach for the isotope analysis of radionuclides. The spectral resolution for the detection of slight shifts can also be enhanced by a temperature reduction using adiabatic expansion. In our previous studies, we reported that the translational temperature was successfully decreased to approximately 180 K in xenon isotope analysis using a supersonic plasma jet. However, there remains a considerable uncertainty regarding the significant temperature reduction compared with the temperature of argon atoms at the edge of the supersonic plasma jet, which is at 790 K. In this study, temperature differences between two species of three mixed gas patterns (neon/argon, argon/strontium, and argon/xenon) were investigated using low-pressure glow discharge plasma. The temperature differences for the mixed gas patterns were clearly observed and are sufficient evidence to support our previous results. The relationship between temperature differences and energy levels of lower states used as absorption transitions is also discussed.