Negative photoion spectroscopy of SF₆ in the inner valence and S 2p energy regions

Negative fragment ion formation from SF₆ has been studied using synchrotron radiation within the energy range 20-205 eV. The fragment ions F^-, F₂^-, S^- and SF^- have been observed. It is shown that shape resonance and unoccupied valence orbitals play an important role in negative ion formation after photoexcitation of inner valence and S 2p electrons. The negative ion yields after photoexcitation of a S 2p core electron show evidence of localization of the shape resonance orbitals around the central S atom. The yields of F^- and F₂^- in the outer valence and inner valence energy regions not only confirm that ion pair formation occurs via predissociating Rydberg states but also demonstrate, for the first time, the importance of intravalence transitions.