Electron Impact Ionization of SFx (x=1-6)

The SF6 molecule plays an important role in many applications. Positive and negative ion formation processes involving SF6 have been studied by many authors and a comprehensive data base exists. On the other hand, no data can be found dealing with the ionization of the SFx (x=1-5) free radicals which are produced in significant quantities when the SF6 molecule is dissociated by collisional interactions. We used the fast-beam technique in a comprehensive series of partial ionization cross section measurements for the SFx (x=1-5) free radicals from threshold to 200 eV. In addition, detailed appearance energy determinations have been carried out to elucidate the break-up mechanism(s) for the formation of the various fragment ions. For each target, the partial cross sections are combined to yield a total ionization cross section which is then compared to predictions based on a semi-empirical modified additivity rule.