Ultrafast dissociation of F 1s excited SF6 probed by electron–ion momentum coincidence spectroscopy

Ultrafast dissociation of the SF6 molecule following F 1s → a*1g excitation has been studied by the coincident measurement of the kinetic energy of the resonantly emitted electron and the momentum of the fragment ion. The nuclear motion takes place on the same time scale as the Auger decay, leading to atomic-like F (1s)-Auger lines in the electron spectrum. De-tuning from the excitation resonance changes the ratio of the two time scales involved. We measured the shift of the atomic-like Auger line and the changes in the parameters that describe the corresponding ionic fragmentation dynamics as a function of the detuning energy. Our data are consistent with predictions based on electron spectroscopic measurements that resolved the Doppler-splitting of the Auger-line. We found that unlike in diatomic molecules a substantial fraction of the excitation energy remains in the neutral fragment(s).