Temperature-enhanced autodetachment from long-lived parent negative ions of gaseous dielectrics

At ambient temperature, T, a number of excellent gas dielectrics attach electrons nondissociatively producing long-lived (autodetachment lifetime > 10-6 s) parent anions. As T is increased above ambient, the dielectric strength of such gas dielectrics was found to decrease this was attributed to the decrease in stable anion formation with increasing temperature. In this paper we report on the effect of T on both the electron attachment and the autodetachment processes in gas dielectrics, which at low energies (< 1 eV) attach electrons predominantly nondissociatively. The reduction in stable parent anion formation at elevated T is principally due to the large increase in autodetachment with increasing T. Results are presented with specific reference to c-C4-F6 (perfluorobutene). The enhanced autodetachment at high T is expected to influence other dielectric gas properties as unstable parent anions become sources of electrons at T above ambient