Carbon dioxide concentration and temperature in flames by raman spectroscopy

The interpretation and prediction of high temperature Raman spectra for CO₂ in flames requires a more detailed treatment of the upper vibrational states than is required for room-temperature spectra. A method for calculating these upper state contributions is presented and is used to evaluate the results of a series of experiments. Laser Raman CO₂ spectra have been obtained for CH₄-air, CO₂ seeded CH₄-air, and CO-air flames. The results indicate that both the high and low temperature CO₂ spectra agree with the theoretical predictions. Comparison of the CO₂ temperature to the N₂ temperature, both measured at the same position in the flames, indicates a better prediction of temperature from the N₂ spectrum than from the CO₂ spectrum. Accurate values for the CO₂ concentrations, however, can be determined from a comparison of the CO₂ spectrum with the N₂ spectrum.