Effect of laser intensity upon density and temperature measurements made with laser-induced predissociative fluorescence

Erhard W. Rothe; Youngwei Gu

doi:10.1117/12.279752

21 November 1997 Effect of laser intensity upon density and temperature measurements made with laser-induced predissociative fluorescence

Erhard W. Rothe, Youngwei Gu

Author Affiliations +

Proceedings Volume 3172, Optical Technology in Fluid, Thermal, and Combustion Flow III; (1997) https://doi.org/10.1117/12.279752
Event: Optical Science, Engineering and Instrumentation '97, 1997, San Diego, CA, United States

Abstract

Laser induced predissociative fluorescence is often used for diagnostics because its short-lived upper states are minimally disturbed by collisions. We discuss here the effects of lower-state collisions using parameters relevant to atmospheric flames. A simple model, with no adjustable parameters, produces a reasonable fit to the data. It predicts that, even at very modest laser energies, the fluorescence intensity is almost directly proportional to the rate constant for rotational energy transfer (RET) within the lower vibrational states. Here we present calculations that show that the ratio of LIPF signals from two rotational states, and thus the deduced temperature, is very sensitive to laser intensity. The conversion of a measured fluorescence ratio to temperature is particularly difficult, because RET rates can be a function of local conditions and of the laser is also important.

Citation Download Citation

Erhard W. Rothe and Youngwei Gu "Effect of laser intensity upon density and temperature measurements made with laser-induced predissociative fluorescence", Proc. SPIE 3172, Optical Technology in Fluid, Thermal, and Combustion Flow III, (21 November 1997); https://doi.org/10.1117/12.279752

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