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Low-Temperature Kinetics of Reactions of OH Radical with Ethane, Propene, and 1-Butene



A B. Vakhtin, J E. Murphy, S R. Leone


The kinetics of the reactions of the OH radical with ethane (k1), propene (k2), and 1-butene (k3) are studied over a temperature range of T = 96-296 K. The low-temperature environment is provided by a pulsed Laval nozzle supersonic expansion of nitrogen with admixed radical precursor and reactant gases. The OH radicals are produced by pulsed photolysis of H2O2 at 248 nm. Laser-induced fluorescence of the OH radicalsexcited in the (1,0) band of the A2ς+-X2 IIi transation is used to monitor the OH decay kinetics to obtain the bimolecular rate coefficients. At T=296 K, the rate constants k1, k2, and k3 are also measured as a function of total pressure. The room-temperature fall-off parameters are used as the basis for extrapolation of the low-temperature kinetic data obtained over a limited range of gas number density, to predict the high-pressure limits of all three rate coefficients at low temperatures. The temperature dependece of the measured high-pressure rate constants for T=96-296 K can beexpressed as follows: K1, difference} = (8.2 1.3)x10-12(T/300) (-0.88 0.20) cmu3^ molecule -1 S-1,K2difference] = (2.95 0.10)x10-11(T/300) (-1.06 0.13) cmu3^ molecule -1S-1, k3difference}= (3.01 0.15) x10-11 (1.44 0.01) cm3molecule-1S-1. All three high-pressure rate constants show a slight negative temperature dependence, which is generally in agreement with both low-temperature and high temperature kinetic data available in the literature. Incorporating the new experimental data on K1 in photochemical models of Saturn's atmosphere may significantly increase the calculated fate photochemical conversion of H2O into C-O containing molecules.
Journal of Physical Chemistry A
No. 47


alkenes, hydroxyl radical, laser induced fluorescence, laval novvle supersonic expangion, low temperature reaction kinetics


Vakhtin, A. , Murphy, J. and Leone, S. (2003), Low-Temperature Kinetics of Reactions of OH Radical with Ethane, Propene, and 1-Butene, Journal of Physical Chemistry A (Accessed June 14, 2024)


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Created October 31, 2003, Updated October 12, 2021