Detection and quantification of hydroperoxides and radicals within stabilized cool flames by means of SVUV-PEPICO spectroscopy

A novel coupling of a stagnation plate burner and the SAPHIRS instrument located at synchrotron SOLEIL has been performed to enable the observation of labile species and radicals within stabilized cool flames. Gases were extracted from a dimethyl ether/O₂/O₃/N₂ cool flame with a capillary probe and expanded through two consecutive skimmers to reach the synchrotron vacuum ultraviolet-photoelectron photoion coincidence spectrometer. threshold photoelectron spectra (TPES) and total ion yields (TIY) were recorded as a function of the photon energy, and led to the identification of species that have so far never been observed in cool flames, including the only expected keto- or aldo-hydroperoxide (hydroperoxymethylformate), hydrogen peroxide, methyl and hydroperoxyl radicals. The quantification of the detected species has been performed and is compared with the predictions of a kinetic model, demonstrating the validity of the experimental approach and suggesting possible ways for improvement.