Measured Lifetime of SF₆^-

The lifetime of the SF₆ anion was measured at the electrostatic ion storage ring ELISA, where decays in the time span from 100   μs to a few seconds were recorded. We find a nonexponential decay with an approximate t^-1.5 power-law dependence. The observed decay rate is accounted for by a model for thermionic emission that takes into account the initial energy spread of the SF₆ molecule prior to electron capture as well as some kinetic energy of the captured electron in the applied plasma-ion source. The energy dependent decay rate is described by an Arrhenius decay constant with a preexponential factor and the electron affinity.