Kinetics following addition of sulfur fluorides to a weakly ionized plasma from 300 to 500 K: Rate constants and product determinations for ion-ion mutual neutralization and thermal electron attachment to SF5, SF3, and SF2

Rate constants for several processes including electron attachment to SF2, SF3, and SF5 and individual product channels of ion-ion mutual neutralization between SF6-, SF5-, and SF4- with Ar+ were determined by variable electron and neutral density attachment mass spectrometry. The experiments were conducted with a series of related neutral precursors (SF6, SF4, SF5Cl, SF5C6H5, and SF3C6F5) over a temperature range of 300-500 K. Mutual neutralization rate constants for SF6-, SF5-, and SF4- with Ar+ are reported with uncertainties of 10-25% and show temperature dependencies in agreement with the theoretical value of T-0.5. Product branching in the mutual neutralizations is temperature independent and dependent on the electron binding energy of the anion. A larger fraction of product neutrals from the SF6- mutual neutralization (0.9 ±0.1) are dissociated than in the SF5- mutual neutralization (0.65 ± 0.2), with the SF4- (0.7 ± 0.3) likely lying in between. Electron attachment to SF5 (k= 2.0 x 10-8 ±12 cm3 s-1 at 300 K) and SF3 (4 ± 3 x 10-9 cm3 s-1 at 300 K) show little temperature dependence. Rate constants of electron attachment to closed-shell SFn species decrease as the complexity of the neutral decreases.