The Underlying Chemistry to the Formation of PO ₂ Radicals from Organophosphorus Compounds: A Missing Puzzle Piece in Flame Chemistry

Abstract Reactive species, such as . PO 2 and HOPO, are considered of upmost importance in flame inhibition and catalytic combustion processes of fuels. However, the underlying chemistry of their formation remains speculative due to the unavailability of suitable analytical techniques that can be used to identify the transient species which lead to their formation. This study elucidates the reaction mechanisms of the formation of phosphoryl species from dimethyl methyl phosphonate (DMMP) and dimethyl methyl phosphoramidate (DMPR) under well‐defined oxidative conditions. Photoelectron photoion coincidence techniques that utilized vacuum ultraviolet synchrotron radiation were applied to isomer‐selectively detect the elusive key intermediates and stable products. With the help of in situ recorded spectral fingerprints, different transient species, such as PO 2 and triplet O radicals, have been exclusively identified from their isomeric components, which has helped to piece together the formation mechanisms of phosphoryl species