Dissociative ionization of methane by 54 eV electron impact

The dissociative ionization process of methane induced by 54 eV electron impact is investigated using an advanced reaction microscope. In the present paper, our attention is specially paid to the kinetic energy distributions of the CH₂⁺, CH⁺ and C⁺ fragments. Energy deposition spectra are presented for these fragments of different kinetic energies. It is shown that the dissociations from the (2a₁)^-1 and (1t₂)^-2(3a₁) states of CH₄⁺ are the dominant contributions of the CH₂⁺, CH⁺ and C⁺ fragments. The kinetic energy of fragment is sensitive to the electronic state of its parent ion. Fragment ions with kinetic energies lower than 0.1 eV are mainly from the dissociation of (2a₁)^-1 state, and partly from the dissociation of (1t₂)^-2(3a₁) state; the ions with energies between 0.1 eV and 0.3 eV are contrituted equally by the two states; the ions with energies higher than 0.4 eV are formed dominantly from the dissociation of (1t₂)^-2(3a₁) state.