Application of the rotational diffusion model to the CARS spectra of high‐temperature, high‐pressure water vapour

Abstract

AbstractCARS spectra of water vapour at elevated pressures (1–16 bar) and temperatures (300–800 K) have been investigated experimentally and theoretically. A theoretical model of the CARS spectrum of water vapour based on Gordon's rotational diffusion model was tested. The model was adapted to include the effects of vibrational relaxation and dephasing processes. Good agreement was found between experiment and theory for all conditions investigated. Rotational inelastic collisions are dominant and contribute approximately 65% to the overall individual molecular linewidths. As part of the data analysis a new measurement of dσ/dω (H2O)=1.10 × 10−34 ± 20% m2 sr−1 has been made.