Comparison of gas temperatures measured by coherent anti-Stokes Raman spectroscopy (CARS) of [O.sub.2] and [N.sub.2]

We investigate the accuracy of temperature measurements by coherent anti-Stokes Raman spectroscopy (CARS) of [O.sub.2] and use measurements taken with [N.sub.2] CARS and a thermocouple for comparison. Scanning vibrational CARS spectra of [O.sub.2] and [N.sub.2] were recorded over a broad range of temperatures: between 294 K and 1900 K in air that wets heated in a tube furnace and at approximately 2450 K in a fuel-lean [CH.sub.4]-[O.sub.2]-[N.sub.2] flame. Temperatures were derived from least-squares fits of simulated and experimental spectra. Both the fundamental vibrational band and the first hot vibrational band were included in fitting. In the case of the tube furnace, the [N.sub.2] and the [O.sub.2] CARS temperature measurements agreed to within 3%, and results were similar with the thermocouple; in the flame the agreement was to within 1%. We conclude that, for cases in which [O.sub.2] is present in sufficient concentrations ([approximately equals]10% or greater), the accuracy of [O.sub.2] thermometry is comparable with that of [N.sub.2]. [C] 2001 Optical Society of America OCIS codes: 120.1740, 300.6230.