Line-mixing and collision induced absorption for O₂-CO₂ mixtures in the oxygen A-band region

The absorption by O₂-CO₂ mixtures in the region of the oxygen A-band near 760 nm has been measured in the laboratory at room temperature and for total pressures up to about 80 atm. As done in our previous studies for O₂-N₂ mixtures the contribution of the "allowed" A-band transitions have been calculated both accounting for line-mixing effects and disregarding this process. The differences between computed spectra and measured values enable extraction of the collision induced absorption (CIA) contribution, which, after removal of the O₂-O₂ contribution, provides, for the first time, the O₂-CO₂ CIA. It is shown that neglecting line-mixing overestimates absorption in the wings and underestimates absorption at the P and R branch peaks, and that the O₂-CO₂ CIA has an integrated intensity, in the A-band region, about 1.5 times larger than that of for pure O₂ and almost 10 times greater than for O₂-N₂.