Flame temperature measurements using the anomalous fluorescence of pyrene

We have evaluated the anomalous fluorescence of pyrene as a method for determining flame temperature. Vapor-phase pyrene was injected into four premixed hydrogen/oxygen flames at equivalence ratios of 1.0 and 1.5 and pressures of 22 and 72 Torr. For each flame, the relative laser-induced (S(2) ? S(0))/(S(1) ? S(0)) emission was monitored as a function of height above the burner and compared to the temperature profile as measured by miniature thermocouples. The thermal behavior of pyrene is discussed in terms of a modified intermediate strong-coupling model. A theoretical calculation of the temperature dependence of the S(2)/S(1) emission ratio agrees well with the experimental flame-temperature data. Based on this agreement, conditions are delineated for the most suitable use of pyrene as a molecular temperature probe.