Line mixing in Raman scattering spectra of CO2 modelled by a non-Markovian Energy-Corrected Sudden approach

Non-Markovian Energy-Corrected Sudden modelling of room-temperature CO₂ Raman scattering spectra up to the far wing is revisited and completed for gas densities between 1 and 45 amagat. The model parameters are fitted on an extended set of low-pressure isolated line widths including very high values of the rotational quantum number J and well reproduce the decreasing of line broadening for the experimentally studied J-values. From calculations of the absolute-intensity rototranslational spectrum at 23 amagat, it is shown that the traditional adiabaticity factor of De Pristo gives a more coherent description of low-pressure line widths and high-pressure wing intensities than the two-parameter factor of Birnbaum–Cohen. A simple qualitative correction of the ECS-modelled intensities for the induced and cross allowed-induced scattering appears to be insufficient to match the experimental data in the spectral wing. Theoretical spectral shapes are also calculated for the O-Q-S branches of vibrotational ν₁ and 2ν₂ Raman bands and compared to experimental results in the density range 1–45 amagat.