Temperature imaging in a supersonic free jet of combustion gases with two-line OH fluorescence

Temperature measurements were performed in a shock-tunnel-generated free jet of hydrogen/oxygen reaction products diluted in argon with a nonsimultaneous, two-excitation-line planar laser-induced fluorescence technique with the hydroxyl radical (OH) as a tracer. Single-shot images were obtained with broadband excitation of isolated transitions in the A(2)Σ(+) ? X(2)Π(1, 0) band of OH near 282 nm, with broadband, temporally integrated detection of the resulting nonresonant emission. A measurement of the fluorescence lifetime in the free jet showed no variation with excited rotational level, allowing the rotational temperature to be obtained from the ratio of single-shot images with laser excitation of different rovibronic transitions.