Concentration measurements are performed in argon–nitrogen and carbon monoxide–nitrogen binary gas mixtures at temperatures of 300 and 900 K at atmospheric pressure using femtosecond coherent anti-Stokes Raman scattering (fs CARS). Polarization suppression of the nonresonant background is also demonstrated for these concentration measurements. Single laser shot measurements at 1000 Hz are performed using a chirped probe pulse to map the temporal evolution of the Raman coherence of each species onto the spectrum of the CARS signal pulse. The pump and Stokes pulses have full width at half-maximum bandwidths of 320 and , respectively and excite Raman transitions with frequencies over a range of . Single laser shot fs CARS spectra are fit using a theoretical model to extract the concentration measurements. For measurements in argon–nitrogen or carbon monoxide–nitrogen gas mixtures, concentration measurements were performed over the range of 5%–90% nitrogen with typical measurement error being less than 2.0% in absolute concentration. The precision of the measurements was typically better than 1.5% in terms of absolute concentration. Nonresonant background suppression clearly revealed the resonant signals from each gas species, and concentration measurements were performed over a slightly reduced concentration range with comparable results.
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