Enhanced methyl-radical production in an Ar-CH₄ pin-hollow cathode discharge

A methyl-radical formation is observed to be enhanced in an Ar-CH ₄ discharge plasma using a hollow cathode with movable pins inside. In the discharge with pins, high energy electrons in the radial edge region of the plasma column produce methyl radicals. They diffuse toward the central region of the plasma column, increasing their density, where the electron temperature is so low (≅0.4 eV) that there occurs no reaction to decrease the methyl-radical density.