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The reaction of methane in the nitrogen afterglow is studied by combination of direct measurements and computer experiment. Theexperimental data were obtained by optical emission spectroscopy of the discharge, by gas chromatography of resulting stable products and by probe diagnostics of charged species in afterglow plasma. The simulation was based on a macroscopic kinetic approach covering 24 species and 61 reactions with input data given by the afterglow experiment. In the present stage of the modelling the initiation of methane conversion was studied. It was found that, contrary to active discharge, in the afterglow plasma the active neutral species (mainly excited dinitrogen molecules) are most important for the dissociation of methane into CH, and H radicals.

A method for the determination of the reduced electric field strength (E/N) in a neon discharge from the optical emission spectra was developed. This method is based on a collisional–radiative model, which was used to calculate the emission spectra of the neon plasma. In the model, populations of 30 excited levels of the neon atom were studied. Various elementary collision processes were taken into account: electron impact excitation, de-excitation and ionization of neon atoms, emission and absorption of radiation, metastable–metastable collisions, metastable and radiative dimer production, Penning ionization, etc. To determine the rates of electron collisions, the Boltzmann kinetic equation for the electron distribution function (EDF) was solved for given E/N, and thus the dependence of the emission spectra on E/N could be determined. The EDF was expanded in terms of Legendre polynomials and the first two terms of this approximation were taken into account. The theoretical emission spectra were fitted by the non-linear least-squares method to the measured spectra with respect to the unknown parameter E/N.The method was applied to the study of low pressure dc glow discharge in neon. In such a discharge the calculated reduced electric field strength could be compared with the independent results of simultaneously performed electric probe measurements of E/N. Generally, close agreement of the calculated values with the experimental data was achieved.