ISSN:
0538-8066
Schlagwort(e):
Chemistry
;
Physical Chemistry
Quelle:
Wiley InterScience Backfile Collection 1832-2000
Thema:
Chemie und Pharmazie
Notizen:
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 CHBr3 at 266 nm is employed for the generation of CH (X2Π) radicals. The CH radical relative concentration is monitored by exciting fluorescence on the R1(2) line of the (A2Δ - X2Π) 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 SF6, 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.
Zusätzliches Material:
3 Ill.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1002/kin.550210905
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