Electron affinities from endothermic negative-ion charge-transfer reactions. IV. SF6, selected fluorocarbons and other polyatomic molecules

Abstract

Exothermic and endothermic negative-ion electron transfer reactions invloving SF6, C6F6, c-C4F8, 2-C4F8, C7F8, c-C6F10 C7F14, C6H5NO2, SiCl4, and SF4 were studied in a tandem mass spectrometer. Cross sections as a function of translational energy were determined for the reactions of various atomic negative ions with most of these molecules. Electron transfer reactions from molecular negative ions were also investigated and in general were found to exhibit very low rate coefficients. Dissociative electron transfer, atom pick-up and ion transfer reactions were observed in competition with electron transfer in several instances. From the translational energy thresholds measured for electron transfer and dissociative electron transfer reactions and from additional bracketing experiments, the following thermodynamic data were derived: E.A. (SF6) ≥ 0.6 ± 0.1 eV; E.A. (SF5) ≥ 2.8 ± 0.1 eV; D0¯(SF5− − F) = 1.1 ± 0.1 ev; E.A. (C6F6) ≥ 1.8 ± 0.3 eV; E.A. (C7F8) ≥ 1.7 ± 0.3 ev; E.A. (c-C6F10) ≥ 1.4 ± 0.3 eV; E. A. (C6H5NO2) ≥ 0.7 ± 0.2 eV.