SHELL STRUCTURE AND SHAPES OF FERMION MICROSYSTEMS - A COMPARATIVE-STUDY OF HE-3 AND NA CLUSTERS

A semiempirical shell-correction method including ellipsoidal deformat ions is used to determine binding energies of open-shell, unpolarized He-3(N) clusters. Shell effects, shapes, and other ground-state proper ties (Like the chemical potential) are determined. He-3(N) clusters ar e found to be substantially Less deformed due to their relatively high surface energy as compared to that of alkali-metal clusters (e.g., so dium clusters), As a result, the size-evolutionary patterns associated with He-3(N) clusters are significantly different than the correspond ing ones for Na-N clusters. In particular, odd-even oscillations and s ignatures of subshell closures are absent in the case of He-3(N) clust ers, while they are prominent in the case of alkali-metal clusters. (C ) 1996 American Institute of Physics.