We experimentally determined complete fallo † curves of the rate constant for the unimolecular decomposition of ethoxy radicals. Two di †erent techniques, laser Ñash photolysis and fast Ñow reactor were used both coupled to a detection of radicals by laser induced Ñuorescence. Experiments were performed at total C 2 H 5 Op ressures between 0.001 and 60 bar of helium and in the temperature range of 391È471 K. Under these conditions the b-CÈC scission (1a)is the dominating decompositionFrom a complete analysis of the experimental fallo † curves the low and the high pressure limiting rate constants of 3.3 ] 10~8 exp([58.5 kJ mol~1/RT ) cm3 s~1 and exp([70.3 kJ k 1a,0 \ [He] k 1a,= \ 1.1 ] 1013 mol~1/RT ) s~1 were extracted. We estimate an uncertainty for the absolute values of these rate constants of ^30%. Preexponential factor and activation energy are signiÐcantly lower than previous estimations. The rate constants are discussed in terms of statistical unimolecular rate theory. Excellent agreement between the experimental and the statistically calculated rate constants has been found. BAC-MP4, QCISD(T), or higher level of theory provide a reliable picture of the energy and the structure of the transition state of this radical bond dissociation reaction. On the same theoretical basis we predict the high pressure limiting rate constant for the b-CÈH scission (1b) of exp([84 kJ CH 3 CH 2 O~] M ] CH 3 CHO ] H~] M k 1b,= \ 1.3 ] 1013 mol~1/RT ) s~1. Atmospheric implications are discussed.

, et al.. Measuring hydroperoxide chain-branching agents during n-pentane low-temperature oxidation. Proceedings of the Combustion Institute, Elsevier, 2017Elsevier, , 36, pp.333 -342. 10.1016Elsevier, /j.proci.2016 AbstractThe reactions of chain-branching agents, such as H2O2 and hydroperoxides, have a decisive role in the occurrence of autoignition. The formation of these agents has been investigated in an atmospheric-pressure jet-stirred reactor during the low-temperature oxidation of n-pentane (initial fuel mole fraction of 0.01, residence time of 2 s) using three different diagnostics: timeof-flight mass spectrometry combined with tunable synchrotron photoionization, time-of-flight mass spectrometry combined with laser photoionization, and cw-cavity ring-down spectroscopy. These three diagnostics enable a combined analysis of H2O2, C1-C2, and C5 alkylhydroperoxides, C3-C5 alkenylhydroperoxides, and C5 alkylhydroperoxides including a carbonyl function (ketohydroperoxides). Results using both types of mass spectrometry are compared for the stoichiometric mixture. Formation data are presented at equivalence ratios from 0.5 to 2 for these peroxides and of two oxygenated products, ketene and pentanediones, which are not usually analyzed during jet-stirred reactor oxidation. The formation of alkenylhydroperoxides during alkane oxidation is followed for the first time. A recently developed model of n-pentane oxidation aids discussion of the kinetics of these products and of proposed pathways for C3-C5 alkenylhydroperoxides and the pentanediones.

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