The relative cross section and kinetic energy distribution of dissociation processes of methane by electron impact

Electron-impact ionization and dissociation of methane (CH4) has been experimentally studied with a cold target recoil-ion momentum spectrometer. We report data for the formation of CHn+ (n = 0 ∼ 3) relative to that of CH4+ as a function of incident electron energy from 20 to 200 eV. Good agreements are achieved with previous studies. The kinetic energy distribution of the recoil-ions is presented and the average kinetic energy released (KER) was obtained for formation of CH3+. Taking advantages of the supersonic jet expansion, the thermal motion contribution to the kinetic energy distribution of the recoil-ions was reduced. The results agree better with theoretical data than those from previous experimental studies. (paper)