Temperature, pressure, and perturber dependencies of line-mixing effects in CO2 infrared spectra. III. Second order rotational angular momentum relaxation and Coriolis effects in Pi <-Sigma bands

The energy corrected sudden approach is used in order to deduce collisional parameters and to model infrared quantities in Pi <-- Sigma bands of CO2-H e and CO2-Ar mixtures in the 200-300 K temperature range. Measured line-bro adening coefficients and absorption in the Q-branch of the nu(2) band at mo derate pressure are first used for the determination (from a fit) of the ti me constant associated with the relaxation of the second order traceless te nsor of the rotational angular momentum (all other collisional quantities h ave been determined previously). The results obtained are consistent with p revious (calculated) temperature dependent values of the depolarized Raylei gh cross sections. The model is then successfully tested through computatio ns of absorption in the nu(2) and (nu(1) + nu(2))(I) bands at elevated dens ities. Analysis of line-mixing effects is made, including study of the infl uence of interbranch transfers and of Coriolis coupling. Differences betwee n the effects of collisions with He and Ar are pointed out and explained. ( C) 1999 American Institute of Physics. [S0021-9606(99)00216-0].