Line broadening coefficients of the CO2–Ar fundamental 3 band are obtained experimentally and theoretically for temperatures from 120 to 765 K. The experimental results are obtained by Fourier-transform infrared spectroscopy. Theoretical values are provided ia quantum-mechanical (close coupling and coupled states) approaches as well as semiclassical (improved Smith–Giraud–Cooper and Robert–Bonamy) methods. The most up-to-date CO2–Ar ab initio intermolecular potential (J. M. Hutson, A. Ernesti, M. M. Law, C. F. Roche and R. J. Wheatley, J. Chem. Phys., 1996, 105, 9130) is employed for all calculations. For all the temperatures probed, theoretical values are found to be in a rather good agreement with experiment. In addition, the Raman Q(j) line broadening coefficients and the application of the random phase approximation are presented.
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The absorption by pure CO2 beyond the ν3 bandhead has been measured with a grating spectrometer. Experiments have been made in the 0–60-bar and 291–751-K pressure and temperature ranges. Our room temperature determinations are in good agreement with previous ones and the measured temperature dependence above room temperature is consistent with recent determinations below 300 K. Lorentzian calculations, modified by the introduction of a line shape corrective factor x, are presented. Good agreement between the observed and calculated spectra is obtained when a temperature independent x factor, determined by Cousin et al. at 296 K, is used.