Temperature dependence of the reactions of CH radicals with NO, NH3 and N2O in the range 200–1300 K
1993; Elsevier BV; Volume: 210; Issue: 1-3 Linguagem: Inglês
10.1016/0009-2614(93)89113-v
ISSN1873-4448
AutoresK. Becker, B. Engelhardt, Harald Geiger, R. Kurtenbach, P. Weisen,
Tópico(s)Spectroscopy and Laser Applications
ResumoBimolecular rate constants for the reactions of CH(X 2Π) radicals with nitric oxide, ammonia and nitrous oxide were measured under pseudo-first-order conditions at 4 Torr total pressure, as a function of temperature in the range 300–1300 K for the CH+NO and CH + NH3 reaction and in the range 200–1250 K for the CH + N2O reaction. CH radicals were generated by excimer laser photolysis of CHClBr2/Ar mixtures and were detected by laser-induced flourescence. The rate constant of the reaction CH+NO was found to be independent of temperature. The measured rate constants of the reactions CH + N2O and CH + NH3 exhibit negative temperature dependences which are described by the following Arrhenius equations (with EA in units of kJ/mol): kCH + N2O (T) = (3.09 ± 0.07) × 10−11 exp[(2.14 ± 0.08)/RT] cm3 s−1, kCH + NH3 (T) = (7.23 ± 0.17) × 10−11 exp[(2.64 ± 0.10)/RT] cm3 s−1 and kCH + NO (T) = (1.87 ± 0.06) × 10−10 exp[(0.00 ± 0.15)/RT] cm3 s−1. All reactions were found to be very fast, with rate constants close to the gas kinetic limit. The negative temperature dependences for the reactions CH + N2O and CH + NH3 are in accord with an addition/decomposition mechanism and are similar to those observed for the reactions of CH radicals with saturated and unsaturated hydrocarbons.
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