Effect of a localized charge on the stability of Van der Waals clusters

The stability of anionic (SF₆)^- _N clusters (in the range of N< 23), generated in asupersonic expansion ion source with electron impact ionization, was investigated bymeasuring their blackbody induced radiative dissociation (BIRD) rates in an electrostaticion beam trap (EIBT) at room temperature. The lifetime traces of EIBT-stored clusters weresubjected to “master equation analysis” and the activation energies, E_a, for the evaporationof a SF₆ monomer wereextracted. We find that the decay rates of (SF₆)^- _N anionic clusters are larger than those of cationic SF⁺ ₅(SF₆)_N-1 measured previously by the same method, and theircorresponding activation energies to be smaller. These observations provide furtherinsight into the effect of localized charge on cluster stability.