Simultaneous temperature and CO2 concentration measurements with multiplex coherent anti-Stokes Raman scattering (CARS) spectra of CO2 were performed. CARS spectra of pure CO2 and various mixtures of CO2 and N2 in a furnace were recorded at various temperatures to test the computer code that simulates CO2 CARS spectra using recent spectroscopic constants. The temperatures obtained from the CO2 CARS spectra were in good agreement with thermocouple temperature measurements. However, the CO2 concentrations cannot be accurately extracted from these spectra. It is believed by the authors that the cross-coherent effect, which has not been included in the present model, and the difficulty of accurately accounting for the background are two important factors affecting the CO2 concentration measurements. H2 pure rotational lines S(4) and S(5) were found in the CO2 CARS spectra of a hydrocarbon flame. These assignments were confirmed from intensity ratio measurements of S(4) and S(5) lines at different temperatures. A theoretical study shows that the H2 concentration measurement from the S(5) line should be more sensitive than that of the S(4) and S(9) lines at the flame temperature. CARS spectra of preanalyzed mixtures of N2, CO2, and H2 in a furnace were recorded to investigate the feasibility of inferring the H2 concentration from these spectra. Simultaneous CO2 and H2 multiplex CARS spectra were also recorded in a CH4/O2 diffusion flame and in the MSU/DIAL test stand to observe the high temperature spectra. The results of these measurements are presented.
© 1991 Optical Society of AmericaFull Article | PDF Article