The measurement of fluorescence lifetimes is important for determining minor-species concentrations in flames when using linear laser-induced fluorescence (LIF). Applications of LIF to turbulent flames require that the quenching rate coefficient be determined in less than approximately 100 μs. Moreover, the measurement technique must be insensitive to the existence of relatively large backgrounds, such as occur from flame emission. To meet these goals, we have recently developed a rapid, gated photon-counting technique, termed LIFETIME. However, for ultimate application to turbulent time-series measurements, LIFETIME must be extended to photon count rates which unfortunately result in nonlinear discriminator operation. In this paper, a correction technique is derived to permit quantitative measurements of fluorescence lifetimes and concentrations at sampling rates up to 4 kHz. The technique was tested against liquid samples having a known lifetime and is further shown to reproduce previous hydroxyl concentration measurements in a series of laminar flames with total photon count rates of up to approximately 35 million detected photoelectrons per second. The fluorescence lifetimes and hydroxyl concentrations are shown to be measured with approximately 10% accuracy (68% confidence interval) for sampling times as low as 25 μs.
|Number of pages||10|
|Journal||Applied Physics B: Lasers and Optics|
|State||Published - Aug 1999|
ASJC Scopus subject areas
- Physics and Astronomy (miscellaneous)
- Physics and Astronomy (all)