Simultaneous measurements of velocity, temperature, and pressure using rapid cw wavelength-modulation laser-induced fluorescence of OH

The beam from a rapid-tuning single-frequency laser was used to probe the R(1)(7) and R(1)(11) A(2)Sigma(+) ? X(2)II (0, 0) line pair of OH at a 45 degrees incident angle in a combustion-driven, supersonic free jet. Absorption line shapes were recorded in spatially resolved, single-point fluorescence. The Doppler shift, intensity ratio, and collisional broadening of the measured line pair were used to determine velocity, temperature, and pressure. The repetition rate of the measurement was 3 kHz.