Plasma-spectroscopic studies on alternating current arc discharges in methane

Plasma spectroscopic studies on alternating current arcs in methane were performed with a view to pyrolytical processes leading to the formation of pyrolytic carbon. Operating parameters such as current intensity, electrode gap and methane filler gas pressure were varied. Excitation temperatures were measured from the rotational levels of CH and C₂ radicals. Temperature determinations were carried out for various arcing periods and in different zones in the plasma column. The validity of the Boltzmann equation was proved. The electron number density was determined from the Stark broadening of the H_β-line.