Plasma-chemical reactions in weakly decomposed CCl4 |
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Authors: | F -W Breitbarth H -J Tiller R Reinhardt |
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Institution: | (1) Department of Chemistry, Friedrich Schiller University, Jena, GDR |
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Abstract: | For the case of weak feed gas decomposition, where the concentration of CCl4 exceeds those of decomposition and built-up products, the emission of CCl* is shown to originate from dissociative excitation of CCl4. With electron concentration measured independently, the kinetics of CCl4 decomposition has been extracted from the time dependence of the CCl* intensity. Supported by EPR determinations of radical concentrations in rapidly flowing CCl4 and CCl4/O2 afterglows, the primary decomposition reaction is shown to be the electron impact dissociation into CCl3 and Cl. Its rate constant (k
1=4×10–8 cm3s–1) indicates strongly that dissociative electron attachment is the main reaction channel at least at r.f. power densities just above the threshold of a self-maintaining discharge. At extremely low mean electron energies the emission of a continuum is observed, which is tentatively ascribed to the radiative CCl3-Cl recombination. |
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Keywords: | Plasma chemistry halocarbon decomposition kinetics |
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