By means of CARS interferometric line shape spectroscopy, the temperature dependences of the broadening coefficients for several Q-branch lines of hydrogen molecules under collisions with water molecules were determined in the temperature range 2100 < T < 3500 K.

We demonstrate the feasibility of a proposed new approach to CARS thermometry with simultaneous measurements of the intensities of the hydrogen Q-branch lines and their linewidths during a single laser shot by means of a spectrograph combined with an interferometer having orthogonal directions of dispersions. This allows correct temperature evaluation that takes into account the directly measured linewidths. The experiments were carried out in a H 2 : N 2 = 1 : 10 mixture in a heated cell at a temperature of 1050 K. The values of the gas mixture temperature, which were defined from dual-broad band (DBB) CARS spectra with linewidth corrections in a pressure range of 2-9 MPa, coincide with thermocouple measurements within ∼2%, while without such a correction, the discrepancies increase up to 5%. The proposed approach can be applied to CARS temperature measurements in investigations of H 2 and hydrocarbon combustions without the necessity of species concentration measurements and not requiring the knowledge of line-broadening coefficients.

A high-resolution spectroscopic method that allows single-shot spectra of Raman-active molecular transitions in non-stationary media to be obtained with a resolution of ∼0.1 cm −1 was developed. The method is based on application of a Fabry-Pérot interferometer to spectral analysis of the CARS signal from Raman transitions with further detection of an interference pattern by a two-dimensional photo-matrix. The implementation of a dual-broadband (DBB) CARS configuration for effective spectral averaging over pump and Stokes laser spectra together with angular averaging of CARS intensities along the complete circumference of Fabry-Pérot interference patterns leads to a significant improvement of interferogram quality, so that nearly all of the single-shot interference patterns obtained for Q-branch lines of the hydrogen molecule in a gas probe volume became suitable for linewidth measurements.

A high-resolution (∼0.1 cm −1 ) spectroscopic method based on the application of a Fabry-Pérot interferometer to the spectral analysis of the coherent anti-Stokes Raman scattering (CARS) signal from an individual Raman transition was used to obtain single-shot spectra of hydrogen Q-branch transitions directly in the flame of a pulsed, high-pressure H 2 /O 2 combustion chamber. Simultaneously with the Fabry-Pérot pattern, a broadband CARS spectrum of the complete H 2 Q -branch structure was recorded in order to measure the temperature of the probe volume. During every cycle of the combustion chamber, a pressure pulse together with single-shot CARS spectra, providing information on individual line shapes and medium temperature, was recorded. On the basis of the experimental data, the temperature dependences of lineshift coefficients for several Q-branch lines of hydrogen molecules under collisions with water molecules were determined in the temperature range 2100 < T < 3500 K, and an empirical 'fitting law' for H 2 -H 2 O lineshift coefficients is proposed.

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