Classical Analysis of Phenomenological Potentials for Metallic Clusters
  The classical trajectories of single particle motion in a Wodds-Saxon and a modified Nilsson potential are studied for axial quadrupole deformation. Both cases give rise to chaotic behaviour when the deformation in the Woods-Saxon and the l**2 term in the modified Nilsson potential are turned on. Important similarities, in particular with regard to the shortest periodic orbits, have been found. 
W.D. Heiss and R.G. Nazmitdinov