Collision-induced population transfer in infrared absorption spectra. III. Temperature dependence of absorption in the Ar-broadened wing of CO₂ ν₃ band

We present experimental and theoretical results on the absorption in the Ar-broadened wing of the infrared CO₂ ν₃ band. Measurements have been made in the 293-765 K temperature range for total gas pressures up to 60 bar and are in good agreement with previous determinations at room temperature. Calculations have been carried out by using a line by line coupling theory presented and tested previously [J. Chem. Phys. 89, 625 (1988) and 91, 2163 (1989)]. The theoretical approach accounts for both line mixing and the wave-number dependence of the relaxation operator. It enables correct modeling of the temperature dependence of absorption. The strong sublorentzian absorption resulting from competitions between negative and positive individual line contributions is analyzed.