Relative fluorescence-quenching measurements of atomic hydrogen in subatmospheric H2/O2/N2 flames with photoionization controlled-loss spectroscopy

Photoionization controlled-loss spectroscopy (PICLS) is developed to obtain relative changes in the fluorescence transition probability (A + Q) under conditions where conventional measurements of the fluorescence lifetime are not feasible. Using PICLS, vertical profiles of relative changes in the transition probability have been measured in 20-torr premixed flat H2/O2/N2 flames under stoichiometric and fuel-rich conditions. These profiles are compared with predictions from kinetic theory, and the implications of this comparison for quantitative fluorescence measurements of atomic hydrogen in flames are discussed. (Author)