QUANTITATIVE CARS SPECTROSCOPY OF THE NU-1 BAND OF WATER-VAPOR

The accuracy of CARS thermometry for H2O vapour has been assessed under carefully controlled conditions for the temperature range 295 to 900 K and the pressure range 0.0066 to 2.7 atm. Excellent agreement between theory and experiment was achieved for line-broadening regimes ranging from Doppler broadening to motional narrowing. Various models for rotational energy transfer and line-broadening were compared and where pressure broadening dominated, excellent agreement was achieved with a simple linewidth model. dependent only on temperature and pressure. Excellent agreement was also achieved using either energy or angular momentum based relaxation models to model motionally narrowed spectra in the pressure range up to 2.7 atm. However, good agreement between theory and experiment depended on the inclusion of state mixing correction factors, and good thermometry accuracy at high temperature was sensitive to the value assumed for the water molecular polarisability.