A laser-induced fluorescence technique, especially suitable for measuring fluctuating temperatures in cold turbulent flows containing very low concentrations of nitric oxide, is described and analyzed. Temperatures below 300 K may be resolved with SNRs of >50:1, using commercially available high-peak-power tunable dye lasers. The method relies on the two-photon excitation of selected ro-vibronic transitions in the NO(A(2)Sigma(+), upsilon' = 0 ? X(2)II, upsilon'' = 0) gamma band. The analysis includes the effects of fluorescence quenching and shows the technique to be effective at all densities below ambient. SNR estimates are based on a preliminary measurement of the two-photon absorptivity for a selected rotational transition in the NO gamma(0,0) band.
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| http://dx.doi.org/10.1364/AO.20.002153 | DOI Listing |
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