Single-pulse gas thermometry at low temperatures using two-photon laser-induced fluorescence in NO-N(2) mixtures.

A technique suitable for measuring fluctuating temperatures in supersonic turbulent flows of N(2) seeded with NO has been demonstrated in a nonflowing cell. The method relies on the two-photon excitation of two selected rovibronic transitions in the NO gamma(A(2)Sigma+,'=0?X(2)II,''=0) band. Measurements between 155 and 295 K in N(2) mixtures containing 300 parts in 10(6) NO were obtained with single-pulse errors below 4% rms.

Two-photon excitation of nitric oxide fluorescence as a temperature indicator in unsteady gasdynamic processes.

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.