ISSN:
1572-8986
Keywords:
Microwave plasma
;
post-discharge
;
CH2 reactivity
;
argon metastable density
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
,
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
,
Technology
Notes:
Abstract This work is devoted to the study of the reactivity of CH 2 radical in the post-discharge of an Ar–CH 4 microwave plasma. These radicals are selectively produced using the energy transfer reaction between argon metastable Ar( 3P2 ) and CH 4 , This paper consists of three parts. The first part is the characterization of the argon metastable source. We measure the absolute argon metastable density within the argon microwave post-discharge, then we select the best discharge parameters in order to obtain the best conditions to produce Ar( 3P2 ) species. The second part is related to the mass spectrometry study of species observed within the post-discharge and produced when methane is injected in an argon microwave post-discharge. We measure the absolute densities of the hydrocarbon species. Results show that the main species observed in the post-discharge are CH 4 , C 2 H 2 then C 2 H 6 , C 2 H 4 and the radical CH 3. However, the radical CH 2 is only detectable for a low CH 4 density injected. The third part is related to the study of the methylene radical (CH 2 ) reactivity in an Ar–CH 4 post-discharge. We measure the reaction rate constant of Ar( 3P2 ) energy transfer to $$CH_4 ;Ar(^3 P_2 ) + CH_4 \underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle\rightarrow}$}}{k} _1 CH_2 + 2H + Ar$$ we find a value k1 ranging from 5.7×10 −16 to 1.2×10 −16 m 3 /s. This value is in good agreement with the results proposed in the literature. Then we use this first reaction to produce CH 2 and to study in post-discharge the reaction $$CH_2 + C^x H_y \underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle\rightarrow}$}}{k} _1 $$ products. In this mechanism C x H y are stable hydrocarbon molecules present in the post-discharge (mainly CH 4 ). We measure the reaction rate constant (k2), which ranges from 5.62×10 −16 to 1.1×10 −15 m 3 /s. These results are discussed, and we propose mechanisms that can explain such a high reactivity.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1023/A:1021797428416
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