Threshold photoelectron spectroscopy in the inner-valence ionization region and photo-double ionization of SF6

The threshold photoelectron (TPE) spectrum of SF6 has been recorded over the photon energy range 25-140 eV using synchrotron radiation and a penetrating-field electron spectrometer. In addition, the photo-double ionization spectrum of SF6 has been obtained over the energy range 30.7-49.3 eV using the threshold photoelectrons coincidence technique. The TPE spectrum in the inner-valence ionization region is found to be significantly different to the conventional photoelectron spectrum in the same binding energy region. Indirect autoionization of neutral Rydberg and shape-resonance states of SFs dominate the formation of the TPE spectrum. Inner-valence SF6+ ion states appear to play a major role in the formation of the SF62+ ion states. The onset of double ionization in SF6 was found to occur at 31.98 +/- 0.02 eV.