New measurements of the thermochemistry of SF5− and SF6−

Abstract Energy-resolved collision-induced dissociation (CID) experiments using a flowing afterglow-tandem mass spectrometer (MS) have been performed on SF 5 − and SF 6 − , two key components of SF 6 -based plasmas. G3/B3LYP and G3(MP2) calculations have also been performed on these systems. The results are compared to other experimental and computational determinations of the thermochemistry of these species. CID of SF 5 − gives a 0 K bond energy of D (SF 4 F − )=2.38±0.10 eV (230±10 kJ mol −1 ). This is in good agreement with the high-level computational results. The threshold for dissociation of SF 6 − (into SF 5 − +F) of 1.85±0.12 eV (178±12 kJ mol −1 ). This dissociation appears to have a barrier greater than the endothermicity, although the barrier is much smaller than that for photodetachment of the same ion.