Line mixing in the nu(1) and 2 nu(2) isotropic Raman Q-branch of CO2 perturbed by argon and helium

The shapes of the nu(1) and 2 nu(2) isotropic Raman Q-branch of CO2 perturb ed by argon and helium have been measured by Stimulated Raman Spectroscopy (SRS) or coherent anti-Stokes Raman Spectroscopy (CARS) techniques. The dat a have been successfully analyzed with an energy corrected sudden (ECS) app roximation model based on basic rates determined independently. Finally com parison of the present data with time resolved double resonance experiments allows us to discuss the physical origin of the two empirical constants wh ich account for the shift and broadening of the branch due to vibrational e ffects. (C) 1999 American Institute of Physics. [S0021-9606(99)00344-X].