Structural properties of screened Coulomb balls
  Small three-dimensional strongly coupled charged particles in a spherical confinement potential arrange themselves in a nested shell structure. By means of experiments, computer simulations and theoretical analysis, it is shown that their structural properties depend on the type of interparticle forces. Using an isotropic Yukawa interaction, quantitative agreement for shell radii and occupation is obtained. 
M. Bonitz, D. Block, O. Arp, V. Golubnychiy, H. Baumgartner, P.   Ludwig, A. Piel, and A. Filinov