Excimer lasers excited by electron or ion beams having energy deposition of 100’s J/ℓ over many microseconds experience a temperature rise of hundreds of degrees (K). The increase in gas temperature may greatly impact both the kinetics and spectroscopic parameters. In this letter we discuss the high-temperature (≤900 K) plasma kinetics and absorption in He and Ne buffered gas mixtures for particle beam pumped XeF lasers. We find both gain and absorption depend differently on gas temperature in these mixtures (absorption decreasing in He mixtures, increasing in Ne mixtures). The differences are attributed to a reduction in diatomic absorbing species with increasing temperature and differences in the temperature dependence of the optical absorption cross sections for NeXe+ and Xe+2.