Kinetics and thermochemistry of electron attachment to SF6

Thermochemical analysis of the electron capture process of SF₆ leads to a rate constant for the reverse process \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm SF}_6^ - \mathop \to \limits^2 {\rm SF}_6 + e^ -,k_2 = 1.5 \times 10^{13 - 31.4/\theta } {\rm s}^{{\rm - 1}} $\end{document}, where θ = 2.303RT, in kcal/mol. The electron affinity of 32±3 kcal/mol is deduced from the observed bimolecularity of the capture process down to 0.1 torr Ar bath gas and estimated entropies of SF₆ and SF. The capture process is discussed from the view point of the formation of a metastable SF electron (SF₆·e) Langevin complex which appears to have a lifetime of about 2 × 10^?13 s. Curve crossing from the SF₆·e complex to vibrationally excited (SF)* appears to have a normal rate and A factor. This is interpreted to indicate near-resonant coupling between the orbiting electron and the vibronic motions of SF₆, together with similarity in structure of SF₆ and SF. It is shown that the apparent slowness of thermal electron ejection from SF is a result of an unfavorable equilibrium constant rather than a slow rate.