New mechanistic insights to the O(3P) + propene reaction from multiplexed photoionization mass spectrometry

Abstract

The reaction of O(³P) with propene (C₃H₆) has been examined using tunable vacuum ultraviolet radiation and time-resolved multiplexed photoionization mass spectrometry at 4 Torr and 298 K. The temporal and isomeric resolution of these experiments allow the separation of primary from secondary reaction products and determination of branching ratios of 1.00, 0.91 ± 0.30, and 0.05 ± 0.04 for the primary product channels CH₃ + CH₂CHO, C₂H₅ + HCO, and H₂ + CH₃CHCO, respectively. The H + CH₃CHCHO product channel was not observable for technical reasons in these experiments, so literature values for the branching fraction of this channel were used to convert the measured product branching ratios to branching fractions. The results of the present study, in combination with past experimental and theoretical studies of O(³P) + C₃H₆, identify important pathways leading to products on the C₃H₆O potential energy surface (PES). The present results suggest that up to 40% of the total product yield may require intersystem crossing from the initial triplet C₃H₆O PES to the lower-lying singlet PES.