State-to-state rotational cross sections in vibrational modes. Application to the infrared Q-branch profile for the (11 10)I←(00 0) 12C16O2 bending band

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Abstract
Direct connection between spectroscopic relaxation cross sections and appropriate state‐to‐state rotational cross sections in vibrational modes enables one to introduce convenient energy corrections to the sudden approximation. Since the angular momentum coupling photon–rotation–vibration is properly taken into account, this approach applies to stretching as well as bending bands. Diode laser experiments have been made for pure 12C16O2 in the infrared Q branch of the (11 10)I←(00 00) band in order to investigate the effect of collisional line mixing on the spectral profile. The energy corrected sudden scaling law is used within the present theoretical approach for both the inversion of j→0 basis cross sections from broadening data and the calculation of line‐coupling coefficients. Resulting absorption profiles are in good agreement with measured values without the need for the introduction of any ad hoc decoupling factor for the considered bending band.