Shell effects on fission barriers of metallic clusters: A systematic description

We use the liquid drop model, with the stabilized jellium model, and the Strutinsky shell correction method [Nucl. Phys. A 95, 420 (1967); 122, 1 (1968)], with the two-center asymmetric deformed harmonic-oscillator potential, to evaluate fission barriers for three representative simple metal clusters (sodium, aluminum, and potassium). We obtain fission barrier heights as a function of size, charge, and mass asymmetry for all possible decay channels of doubly charged clusters with up to 30 atoms. We show how fragment deformations change the barrier height. For small sodium and potassium clusters we find good agreement of the fission barriers with molecular-dynamics calculations. The critical number (cluster size for which fission competes with evaporation) is correctly reproduced for doubly charged clusters of the three metals considered.