Kinetic measurements on methylidyne radical reactions with several hydrocarbons at low temperatures

The temperature dependences of the methylidyne radical reactions with methane, allene, methylacetylene and propene were studied. This work was carried out in a supersonic flow reactor coupled with pulsed laser photolysis (PLP) and laser-induced fluorescence (LIF) techniques. Three Laval nozzles were...

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Published in:Physical chemistry chemical physics : PCCP 2005-01, Vol.7 (15), p.2921-2927
Main Authors: DAUGEY, Nicolas, CAUBET, Philippe, RETAIL, Bertrand, COSTES, Michel, BERGEAT, Astrid, DORTHE, Gérard
Format: Article
Language:English
Subjects:
Alkadienes - chemistry
Alkenes - chemistry
Alkynes - chemistry
Argon - chemistry
Chemical Sciences
Chemistry
Cold Temperature
Exact sciences and technology
Free Radicals - chemistry
General and physical chemistry
Hydrocarbons - chemistry
Hydrocarbons, Brominated - chemistry
Kinetics
Lasers
Methane - chemistry
Nitrogen - chemistry
or physical chemistry
Photochemistry
Photolysis
Physical chemistry of induced reactions (with radiations, particles and ultrasonics)
Spectrometry, Fluorescence
Temperature
Theoretical and
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Summary:The temperature dependences of the methylidyne radical reactions with methane, allene, methylacetylene and propene were studied. This work was carried out in a supersonic flow reactor coupled with pulsed laser photolysis (PLP) and laser-induced fluorescence (LIF) techniques. Three Laval nozzles were designed to provide uniform supersonic expansions of nitrogen at Mach 2 and of argon at Mach 2 and 3 to reach low temperatures, e.g. 170, 128 and 77 K, respectively. CH radicals were produced by PLP of CHBr3 at 266 nm and probed by LIF. The exponential decays of the CH fluorescence were acquired, hydrocarbons being introduced in excess. The rate constants for the CH+CH4 reaction are in good agreement with the temperature dependence proposed by Canosa et al. (A. Canosa, I. R. Sims, D. Travers, I. W. M. Smith and B. R. Rowe, Astron. Astrophys., 1997, 323, 644-651, ) i.e. 3.96x10(-8)(T/K)(-1.04) exp(-36.1 K/T) in the range 23-298 K. The rate constants of the CH+C3H4(allene), CH+C3H4(methylacetylene) and CH+C3H6(propene) reactions exhibit a small temperature dependence between 77 and 170 K, with a maximum rate around 100 K close to (4.3-4.6)x10(-10) cm3 molecule-1 s-1.
ISSN:1463-9076
1463-9084
DOI:10.1039/b506096f