Collisional Narrowing and Spectral Shift in CARS Spectra of Molecular Nitrogen and Oxygen at Pressures up to 2500 bar and Temperatures of 850 K

Abstract

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