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 R1(7) and R1(11) A2Sigma(+) - X2Pi(0,0) line pair of OH at a 45-deg 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.