Temperature dependence of electron attachment and detachment in SF ₆ and c-C₄F₆

In the temperature, T, range of 300-600 K and the mean electron energy range ⟨ε⟩ of 0.19-1.0 eV, the total electron attachment rate constant for SF₆ and C-C₄F₆ measured in dilute mixtures with N₂, is virtually independent of T. Under the same experimental conditions the stabilized SF₆^- anion does not undergo autodetachment but the stabilized c-C₄F ₆^- anion undergoes a profound increase in autodetachment (by about four orders of magnitude). This difference between the SF ₆^- and the c-C₄F₆^- anions is attributed to the larger electron affinity of the SF₆ molecule compared to the c-C₄F₆ molecule. The heat-activated autodetachment for c-C₄F₆^- is related to increases in the internal energy content of the c-C₄F ₆^- anion and is found to have an activation energy of 0.237 eV. The "limiting electric field strength" of SF ₆ was found to increase by ∼ 11% as T was increased from 300 to 600 K.