Degenerate four-wave mixing of S2 and OH in fuel-rich propane/air/SO2 flames

Absorption spectroscopy (AS) is here used in conjunction with degenerate four-wave mixing (DFWM) to determine the absolute concentration profiles of S2 and OH in a premixed propane/air/SO2 flame at atmospheric pressure. While relative concentrations of OH and S2 are mapped by taking advantage of the high sensitivity of the DFWM technique, AS is used to obtain an absolute number density of OH at flame positions where a significant level of this radical occurs. The relative S2 profile obtained by DFWM is put on an absolute scale via quantitative comparison with the OH profile. (AIAA)