Dynamic coexistence of various configurations: clusters vs.nuclei
  The presence of energy shells in metallic clusters and atomic nuclei leads to a peculiar relation between the number of particles N and the structure, and this leads to a strong correlation between the energy spectrum and N. An analysis of experimental data leads to the conclusion that, in addition to the static Jahn-Teller effect, the dynamic effect leading to the quantum coexistence of different configurations (quantum oscillations) plays an important role. Such suggested coexistence is an essential feature of clusters as well as nuclei, both finite Fermi systems. 
V.Z.Kresin and J.Friedel
cond-mat.mes-hall nucl-th