We investigate the accuracy of temperature measurements by coherent anti-Stokes Raman spectroscopy (CARS) of O<sub>2</sub> and use measurements taken with N<sub>2</sub> CARS and a thermocouple for comparison. Scanning vibrational CARS spectra of O<sub>2</sub> and N<sub>2</sub> were recorded over a broad range of temperatures: between 294 K and 1900 K in air that was heated in a tube furnace and at approximately 2450 K in a fuel-lean CH<sub>4</sub>–O<sub>2</sub>–N<sub>2</sub> 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</sub> and the O<sub>2</sub> 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</sub> is present in sufficient concentrations (≈10% or greater), the accuracy of O<sub>2</sub> thermometry is comparable with that of N<sub>2</sub>.
© 2001 Optical Society of America
Thomas A. Reichardt, Paul E. Schrader, and Roger L. Farrow, "Comparison of Gas Temperatures Measured by Coherent Anti-Stokes Raman Spectroscopy (CARS) of O2 and N2," Appl. Opt. 40, 741-747 (2001)