Measurements of the effective lifetime of O atoms in atmospheric premixed flames

The effective lifetimes of the 2p33p3P and the 2p33p5P states of atomic oxygen have been measured to be 290 ± 80 and 250 ± 80 ps, respectively, in the recombination zone of a H2/O2 flame at atmospheric pressure. Measurements were also performed in different zones of the H2/O2 flame and in the recombination zone of a N2O/H2 flame. Laser pulses with a duration of 35 ps and a wavelength of 225.6 nm excited the atoms by a two-photon absorption process. Lifetimes were deduced from time-resolved recordings of the fluorescence at 845 and 777 nm using a fast photomultiplier tube.