Two-wavelength CARS thermometry based on S-branch rotational transitions in the hydrogen molecule

An investigation was made of the capabilities of a two-wavelength CARS thermometry method based on determination of the integral intensities of rotational lines resulting from the S(1) and S(3) Raman transitions in the hydrogen molecule. The gas temperatures were measured in a heated cell and in a hydrogen–air burner at atmospheric pressure. An analysis was made of the factors governing the precision of temperature measurements in a time equal to the duration of one laser pulse (≈10 ns). The relative standard deviation Σ_T of the temperatures in a heated cell, measured with the aid of 300 laser pulses, was 1.5% at T=296 K and 8% at T=1000 K; for the measurements on the burner this deviation was 11% at ≈1400 K.