Fragmentation dynamics of ionized argon clusters: an effective potential model

A dynamical model based on an effective potential is employed to describe metastability and the related time scales for evaporation processes in ionized Argon clusters (Ar) _n ⁺ , withn from 6 up to 27. The effective interaction, and its dependence on the cluster size, is obtained by combining previous ab initio results and Monte Carlo simulations for the above systems with an assumed linear variation of the cluster volume with then number of monomers. The overall metastability of the excited clusters is linked to the possible local rotational ‘temperature’ of such species and the distributions of the ensuing lifetimes are analysed as function of cluster size and of different nucleation mechanisms. It is found that an unusually large range of lifetime values is obtained from the present modelling, in general accord with earlier experiments, and that the existence of large rotational barriers can markedly delay the dissociation of metastable species.