FRAGMENTATION PHASE-TRANSITION IN ATOMIC CLUSTERS-II - SYMMETRY OF FISSION OF METAL-CLUSTERS

We present a statistical fragmentation study of doubly charged alkali (Li, Na, K) and antimony clusters, The evaporation of one charged trim er is the most dominant decay channel (asymmetric fission) at low exci tation energies. For small sodium clusters this was quite early found in molecular dynamical calculations by Landman et al. [1]. For doubly charged lithium clusters, we predict Li-9(+) to be the preferential di ssociation channel. As already seen experimentally a more symmetric fi ssion is found for doubly charged antimony clusters. This different be havior compared to the alkali metal clusters is in our model essential ly due to a larger fissility of antimony. This is checked by repeating the calculations for Na-52(++) with a bulk fissility parameter set ar tificially equal to the value of Sb.