Structure of mesoscopic Coulomb balls
  An analysis of the structural properties of three-dimensional Coulomb clusters confined in a spherical parabolic trap is presented. Based on extensive high accuracy computer simulations the shell configurations and energies for particle numbers in the range $60 \le N\le 160$ are reported. Further, the intrashell symmetry and the lowest metastable configurations are analyzed for small clusters and a novel type of excited state which does not involve a change of shell configuration is identified. 
P. Ludwig, S. Kosse, and M. Bonitz