The Onset of Chaos with a Quadrupole--Quadrupole Interaction
  The transition from order to chaos in atomic nuclei has been studied analytically and numerically using a quadrupole--quadrupole residual interaction. This interaction leads to chaotic behaviour, but the critical energy $E_C\simeq 12.6$ MeV, corresponding to the onset of chaos, is higher than that of the experimental one. 
V.R. Manfredi, L. Salasnich