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Publisher Summary Intensities of Rayleigh and Raman-scattered radiation from a laser beam traversing a fluid are independent of the velocity of the scattering molecules. It is found that for Rayleigh scattering, either under conditions where the scattering cross section does not vary appreciably from species to species or where no appreciable change in the concentration-weighted mean value of the cross section occurs with chemical reaction, values of gas temperature can be found from density measurements and the equation of state, if one can assume constant pressure or known pressure variations. Vibrational Raman scattering has been successfully used to determine temperature in a wide variety of laboratory-scale flows, including combustion systems. The main disadvantages of Raman diagnostics for temperature are the weakness of the Raman effect, which limits applications to moderately clean systems, and the care necessary to set up precision optical systems with adequate optical access. It is found that where the value of the measurements warrants even greater experimental complexity, highly luminous and/or particle-laden systems can be probed for temperature by coherent anti-Stokes Raman spectroscopy. |
