Kinetics and thermochemistry of electron attachment to SF6

Abstract

AbstractThermochemical 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.