Doubly ionized states of CH 4 studied by double‐charge‐transfer and auger‐electron spectroscopies

High‐resolution double‐charge‐transfer spectroscopy has been used to measure the double‐electron‐capture reactions with CH 4 . Using kilo electron volt OH + , CI + and F + projectile ions it is possible in double‐electron‐capture reactions with CH 4 molecules to populate the ground triplet state of CH   4 2+ . The energy of this state relative to the gound state of CH 4 is found to be 38.2±0.4 eV, while the fiest excited triplet state is found at a double‐ionization energy of 46.7±0.8 eV. In double‐electron‐capture reactions involving H + projectile ions and CK 4 molecules, low‐lying singlet states of CH   4 2+are populated. The energies of the four lowest singlet states in CH   4 2+were measured to be 39.2±0.4, 40.5±0.4, 42.1±1 and 51.0±1 eV. High‐resolution photon‐induced Auger‐electron spectra of the CH 4 molecule have been recorded. The KLL Auger Spectrum shows four distinct structures in the 30–70 eV double‐ionization evergy range centred at 40.3±0.1, 47.03, 53.2±0.3 and 6.9±0.3 eV. The previously published data on CH   4 2+have been reviewed.