Methane decomposition in glow-discharge at sub-Torr pressure*

This work presents the investigation results of a normal glow discharge conducted in Ar-CH₄ and Ar-CH₄-H₂ mixtures. The discharge is performed in gas at a pressure of P=0.4-1 Torr and is characterized by a lack of a positive column. This study focused on measuring products of methane decomposition, such as C₂, CH, and H using a planar laser-induced fluorescence approach. The emerging results show a high hydrogen atom density, indicating a high degree of methane decomposition of up to 20%. The decomposition is sustained by high electron density, validated by the analysis of Stark broadening of hydrogen Balmer lines. These results are important in positioning the glow discharge as a very potent plasma source for methane decomposition. Additionally, the absolute densities of several species measured in this work are useful for benchmarking plasma-chemistry simulations.