An experimental program aimed at development of a laser-based technique for non-intrusive in-situ measurement of the hydroperoxy radical (HO2), a reaction intermediate which controls the rate of hydrocarbon oxidation in the intermediate temperature regime and which is important in hydrocarbon combustion in general, will be carried out. The technique utilizes the non-linear interaction between a light source and an absorbing medium called degenerate four-wave mixing (DFWM). An existing laser system will be tuned to interact with a low lying electronic transition which is unique to HO2. This spectroscopic feature does not have the spectroscopic interference problems of other methods proposed for measurement of HO2. The program will consist of four major tasks: (1) assembling a reliable, quantifiable HO2 source; (2) developing a ClO titration scheme for quantification; (3)measuring HO2 concentrations produced by the calibrated source for definition of spectroscopic constants and effects of such parameters as pressure, temperature, etc; (4) measuring HO2 in a flow reactor and a flame facility. Successful completion of this program will provide a new diagnostic tool to probe hydrocarbon oxidation and to provide new insight into the chemistry which limits efficiency and controls emissions from hydrocarbon combustion systems.
