nu i13/2 structures in Sm-155 and Gd-159: Supporting evidence of a Z=60 deformed subshell gap

Maximal ground-state deformation should occur when both proton and neutron Fermi surfaces are located at midshell. However, subshell gaps that stabilize large deformation can exist at proton or neutron values other than midshell. One such gap may occur at Z = 60 in the rare-earth region, as the energy of the first 2+ states in even-even nuclei are often lowest in an isotonic chain for neodymium (Z = 60) rather than the midshell isotopes of dysprosium (Z = 66). Further evidence of this deformed gap has now been observed by investigating the signature splitting systematics of the nu i13/2 bands found in the odd-N, rare-earth nuclei. These were aided by the present observation of the nu i13/2 band in 159Gd and the confirmation of the same structure in 155Sm via the transfer of a neutron from a 160Gd beam to a 154Sm target.