Comparison of calculated and experimental thermal attachment rate constants for SF6 in the temperature range 200-600 K.

Electron attachment cross-sections are calculated for the process e + SF6 → SF 6 – in the energy range 1–200 mi11ie1ectron volts. A local e1ectron-scattering approximation [1,2] is used in which diatomic-like potential energy curves near the equilibrium SF6 ground state are constructed from recent spectroscopic data. Good agreement is found with experimental attachment cross-sections [3,4] at a temperature of 300K. The same calculation, with appropriate adjustment of the thermal populations, is used to calculate attachment rate constants in the range 50–600K. An additional cross-section contribution from the channel e + SF6 → SF 5 – + F, obtained from experimental data of others, is then added to the SF 6 – /SF6 channel cross-section and comparisons made with measured rate constants [5–7] in the range 200–600K. An estimate of the photodetachment energy of SF 6 – (X2Alg) is also given.