Line mixing in the ν₁ and 2ν₂ isotropic Raman Q-branch of CO₂ perturbed by argon and helium

The shapes of the ν₁ and 2ν₂ isotropic Raman Q-branch of CO₂ perturbed by argon and helium have been measured by Stimulated Raman Spectroscopy (SRS) or coherent anti-Stokes Raman Spectroscopy (CARS) techniques. The data have been successfully analyzed with an energy corrected sudden (ECS) approximation model based on basic rates determined independently. Finally comparison of the present data with time resolved double resonance experiments allows us to discuss the physical origin of the two empirical constants which account for the shift and broadening of the branch due to vibrational effects.