Pressure broadening and line coupling in bending bands of CO2

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Abstract
The pressure broadening and line coupling cross sections in the Fano–Ben Reuven theory of line shapes are calculated for bending bands of CO2 in a bath of He atoms. Molecular collision dynamics are simplified by invoking the infinite order sudden (IOS) approximation for molecular rotational and vibrational angular momentum in a manner similar to but not identical with the method developed by Clary and shown to be accurate for CO2–He. Numerical values are obtained using a pairwise additive interaction potential developed by Clary. Predictions are in good accord with data for various infrared bands and pure rotational Raman spectra. It is found that all the pressure broadening and state‐to‐state cross sections depend on only a few dynamical factors (generalized IOS cross sections) and are therefore closely interrelated. Results are used to assess models developed previously to analyze line shapes in this and similar systems.