Shape coexistence in the mass A = 130 region

The mass A = 130 region extends from the region around the double magic nucleus 132Sn into the deformed region below N = 82 and above Z = 50. In the transitional region between spherical and deformed shapes many nuclei are very soft and dramatic shape changes and coexisting shapes are likely to appear. In this mass region the proton Fermi surface lies close to the bottom of the h11/2 intruder shell and the neutron Fermi surface in the upper part of the same subshell. Therefore, proton excitations to this subshell will favor prolate shapes, whereas neutrons excitations to the same shell will favor triaxial or oblate shapes. This leads to phenomena like coexisting neutron and proton s-bands in even-even nuclei and to large deformation changes in h11/2 bands in both odd-N and odd-Z nuclei when a pair of the other kind of nucleons align