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Kinetics of CH radical reactions with N 2 O, SO 2 , OCS, CS 2 , and SF 6
Author(s) -
Zabarnick S.,
Fleming J. W.,
Lin M. C.
Publication year - 1989
Publication title -
international journal of chemical kinetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.341
H-Index - 68
eISSN - 1097-4601
pISSN - 0538-8066
DOI - 10.1002/kin.550210905
Subject(s) - chemistry , arrhenius equation , radical , dissociation (chemistry) , photodissociation , kinetics , reaction rate constant , chemical kinetics , analytical chemistry (journal) , laser induced fluorescence , flash photolysis , fluorescence , kinetic energy , activation energy , photochemistry , physics , organic chemistry , quantum mechanics , chromatography
Abstract Pulsed laser photolysis/laser‐induced fluorescence (LIF) is utilized to measure absolute rate constants of CH radical reactions as a function of temperature and pressure. Multiphoton dissociation of CHBr 3 at 266 nm is employed for the generation of CH (X 2 Π) radicals. The CH radical relative concentration is monitored by exciting fluorescence on the R 1 (2) line of the (A 2 Δ – X 2 Π) transition at 429.8 nm. A resistively heated cell allows temperature studies to be performed from room temperature to ≈670 K. The following Arrhenius equations are derived:\documentclass{article}\pagestyle{empty}\begin{document}$${\rm CH}\,{\rm + }\,{\rm N}_{\rm 2} {\rm O,}\,\,\,\,\,\,\,\,k = (1.59 \pm 0.20)\, \times \,\,10^{ - 11} \,\,\exp [(500 \pm 45)/T]{\rm cm}^{\rm 3} {\rm s}^{{\rm - 1}};$$\end{document}\documentclass{article}\pagestyle{empty}\begin{document}$${\rm CH}\,{\rm + }\,{\rm SO}_{\rm 2} {\rm ,}\,\,\,\,\,\,\,\,k = (1.32 \pm 0.17)\, \times \,\,\,10^{ - 10} \,\,\exp [(250 \pm 45)/T]\,\,{\rm cm}^{\rm 3} {\rm s}^{{\rm - 1}};$$\end{document}\documentclass{article}\pagestyle{empty}\begin{document}$${\rm CH}\,{\rm + }\,{\rm OCS,}\,\,\,\,\,\,\,\,k = (1.99 \pm 0.11)\, \times \,\,\,10^{ - 10} \,\,\exp [(190 \pm 20)/T]\,\,{\rm cm}^{\rm 3} {\rm s}^{{\rm - 1}};$$\end{document}\documentclass{article}\pagestyle{empty}\begin{document}$${\rm CH}\,{\rm + }\,{\rm CS}_{\rm 2} {\rm ,}\,\,\,\,\,\,\,\,k = (3.49 \pm 0.36)\, \times \,\,\,10^{ - 10} \,\,\exp [- (40 \pm 35)/T]\,\,{\rm cm}^{\rm 3} {\rm s}^{{\rm - 1}};$$\end{document}\documentclass{article}\pagestyle{empty}\begin{document}$${\rm CH}\,{\rm + }\,{\rm SF}_{\rm 6} {\rm ,}\,\,\,\,\,\,\,\,k < 5\,\,\, \times \,\,\,10^{ - 17} {\rm cm}^{\rm 3} {\rm s}^{{\rm - 1}} .$$\end{document} With the exception of SF 6 , the reactions of sulfur containing species proceed at rates that are near the theoretical gas kinetic collision frequency. Additionally, these reactions all have activation energies that are near zero or slightly negative. These observations are consistent with an insertion‐decomposition mechanism being dominant under these conditions.