Electron-impact dissociative ionization of SF6 studied by angle-resolved (e, e+ion) spectroscopy

We study the electron-impact dissociative ionization of SF6 using a scattered electron-ion coincidence technique. The ion-yield spectra are obtained at an incident electron energy of 1.4 keV for scattering angles ranging from 2.2∘ to 8.2∘ to investigate the momentum transfer dependences of the fragment-ion yields and shape resonance features. It is found that the 4t1u→ɛt2g resonance is evident over a wide momentum transfer range, indicating its strong influence on the SF3+ production by electron impact, while resonance bands in the SF5+ and SF4+ yield spectra rapidly diminish with increasing momentum transfer. In addition, the angular distribution of SF5+ reveals the significant difference in stereodynamics between electron-impact-induced and photon-induced ionization of SF6. We also discuss the dissociation mechanisms of SF6+ using the kinetic energy distributions of the fragment ions. Analysis of the data strongly suggests that many of the SF6+ ions in the DT2g2 state decay by internal conversion to a lower electronic state and dissociate to SF5++F, followed by statistical emission of F or F2.