Formation and dissociation of doubly ionized methane

Translational energy spectra of H− ions arising from double charge transfer to 1.5–7.0 keV protons from methane have been recorded and interpreted as the single and double ionization spectra of CH4. The excited states of CH++4 are not resolved, but a large broad peak of 4 eV half-width is observed, starting at around 35 eV, with a long tail extending to 44 eV. The peak maximum is at 38.6 eV. Four dissociation reactions of CH2+4 have been observed using photoion–photoion coincidence techniques with Heii light. All the principal discrepancies in comparisons between the experimental and theoretical work on CH2+4 can now be reconciled.