Production of CH(A²Δ) radicals from the dissociative excitation reaction of C₂H₂with microwave discharge flow of Ar

Abstract

Optical emission spectra of the CH(A2Δ–X2Π) transition were observed using the dissociative excitation reaction of C2H2 with the microwave discharge flow of Ar at the pressure of Ar, PAr, in the range of 0.20–0.40 Torr. The mechanism of the production of the CH(A2Δ) state was investigated by the following two methods. The first is the comparison of the PAr dependences of the emission intensity, of the intensity of the laser-induced fluorescence spectra of the 3P1–3P0 transition of Ar, and of the density and temperature of free electrons. The second is the steady-state chemical kinetic analysis with several assumptions of the relevant reaction rate constants. It was concluded that CH(A2Δ) radicals were formed by charge transfer from Ar+ followed by ion–electron recombination with the significant contribution of the impact of free electrons. Energetic considerations revealed that the ions participating in the recombination reaction are excited vibrational levels of C2H2+.

Cross Sections for Electron Collisions with Acetylene

“…For example, plasma can be used to make HCCH from coal, 1 natural gas, 2 and methane. 3,4 Conversely acetylene plasmas are used for a variety of chemistries; 5 they are used to make C 2 , 6 CH*, 7 fullerenes, 8 diamonds, 9 carbon nanoparticles, 10 hydrocarbon nanoparticles, 11 nanotubes, 12,13 and polymers, 14 as well as other chemical processes. 15,16 Acetylene plasmas are used to provide a variety of different coatings.…”