Correlation between nuclear motion in the core-excited CF₄ molecule and molecular dissociation after resonant auger decay

Dissociation of the CF⁺₄ molecular ion has been investigated using monochromatized synchrotron radiation and the energy-selected electron-ion coincidence method. The 2t^{− 1}₂ C ionic state produces fragment ions CF⁺₂ and CF⁺₃. The branching ratio CF⁺₂/CF⁺₃ is increased by a factor of ˜6 by the C 1s excitation to the lowest unoccupied antibonding orbital, from the ratio at the direct ionization of the 2t⁻¹₂ orbital. This increase is interpreted in the light of the nuclear motion in the core-excited state, with the help of theoretical calculations based on the vibronic model.