High-T measurements in reflected shock waves of rate constants for D + CH3 and D + H2 : comparisons with theory.

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D-atom atomic resonance absorption spectrometric (ARAS) detection has been used to study the thermal decomposition of C{sub 2}D{sub 5}I to give C{sub 2}D{sub 5}-radicals in {approx}70% yield (924-1370 K). C{sub 2}D{sub 5} then decomposes to give C{sub 2}D{sub 4} + D effectively instantaneously on the time scale of the bimolecular kinetics experiments. The concurrent thermal decompositions of both C{sub 2}D{sub 5}I and CH{sub 3}I can then be used to prepare well-defined initial concentrations of both D-atoms and CH{sub 3}-radicals. Experiments were performed by observing absolute [D] depletion and [H] formation. The results were initially modeled with a 33 step mechanism; ... continued below

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Michael, J. V.; Su, M.-C. & Sutherland, J. W. July 9, 2002.

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D-atom atomic resonance absorption spectrometric (ARAS) detection has been used to study the thermal decomposition of C{sub 2}D{sub 5}I to give C{sub 2}D{sub 5}-radicals in {approx}70% yield (924-1370 K). C{sub 2}D{sub 5} then decomposes to give C{sub 2}D{sub 4} + D effectively instantaneously on the time scale of the bimolecular kinetics experiments. The concurrent thermal decompositions of both C{sub 2}D{sub 5}I and CH{sub 3}I can then be used to prepare well-defined initial concentrations of both D-atoms and CH{sub 3}-radicals. Experiments were performed by observing absolute [D] depletion and [H] formation. The results were initially modeled with a 33 step mechanism; however, because of the high sensitivity for H- and/or D-detection, the mechanism could be reduced to four reactions, all of which are known except the exchange reaction, D + CH{sub 3} {yields} CH{sub 2}D + H. The rate constants were found to be temperature independent with k = (2.20 {+-} 0.22) x 10{sup -10} cm{sup 3} molecule{sup -1} s{sup -1} for 1294 {le} T {le} 1753 K. The present data have been combined with earlier lower temperature determinations, and the resultant database has been compared with unimolecular rate theory results. From theory, k = kk{sub {infinity}}<k{sub f{var_epsilon}}/(k{sub f{var_epsilon}} + k{sub f{var_epsilon}})> = k{sub {infinity}}F. Using the frequencies and structures given in Seakins et al. and Sutherland et al., we find F(300 K) is 0.928 (in good agreement with Seakins et al.), and at higher-T, F(1800 K) = 0.857. Klippenstein, Goergievski, and Harding find, from recent extensive theoretical calculations, values for F varying from 0.92 to 0.79 over the same T-range. Reliable values for the high-pressure limiting rate constant for methane dissociation at high-T can now be inferred from the present study.

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  • 17th International Symposium on Gas Kinetics, Essen (DE), 08/24/2002--08/28/2002

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  • Report No.: ANL/CHM/CP-108175
  • Grant Number: W-31-109-ENG-38
  • Office of Scientific & Technical Information Report Number: 799851
  • Archival Resource Key: ark:/67531/metadc741904

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  • July 9, 2002

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  • Oct. 19, 2015, 7:39 p.m.

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  • March 24, 2016, 10:27 p.m.

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Michael, J. V.; Su, M.-C. & Sutherland, J. W. High-T measurements in reflected shock waves of rate constants for D + CH3 and D + H2 : comparisons with theory., article, July 9, 2002; Illinois. (digital.library.unt.edu/ark:/67531/metadc741904/: accessed August 20, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.