On the fission of charged alkali-metal clusters

A deformed jellium model is used to calculate the fission barrier height of Na-24(2+) --> Na-21(+) + Na-3(+) within the Kohn-Sham density-functional theory (i.e., including shell effects). Although the shape of the barrier obviously depends on the parametrization of the fission path, we have found that the saddle point corresponds to a configuration in which the emerging fragments are already formed and rather well apart. From this result, we offer a simple way to calculate the barrier height for charged trimer emission from alkali-metal clusters of (almost) arbitrarily large size and charge state.