Breakdown Curves for Polyatomic Negative Ions

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Abstract
Negative‐ion breakdown curves were obtained at low (0–1 eV) energies for SF6 and a number of fluorocarbons. The dissociation rate constants, as a function of internal energy of the parent negative ions, were computed for the processes observed and used to estimate kinetic shifts and thermochemical appearance potentials, at 0°K, for the fragments. The results (e.g., metastable curve widths and temperature effects) were found to be in agreement with the quasiequilibrium theory (QET) of mass spectra. It is predicted that most of the parent negative ions studied (e.g., C7F14− from perfluoromethylcyclohexane) would not fragment if formed by the capture of a thermal electron by the vibrationally cold molecule.