COLLISIONAL NARROWING AND SPECTRAL SHIFT IN CARS SPECTRA OF MOLECULARNITROGEN AND OXYGEN AT PRESSURES UP TO 2500 BAR AND TEMPERATURES OF 850-K

Vibrational-rotational CARS spectra of molecular nitrogen and oxygen a t high densities and temperatures are recorded using a scanning CARS-s pectrometer. Measurements are performed at pressures up to 2500 bar an d temperatures up to 850 K. The spectral line position and halfwidth o f the fully collapsed Q-branch are determined for pure N2, O2, N2/O2 M ixtures and Ar/O2 mixtures. Comparisons of the experimental data with different theoretical models for the rotational energy transfer are al so presented. Three quantum mechanical approaches (MEG-, ECS-, PEG-law s) are compared with a classical description of the relaxation process treating the angular momentum as a continuous variable.