Deformation of 126Ce

Abstract The gamma decays of excited states in the nucleus 126 Ce have been identified in a study of the 92 Mo( 40 Ca, α2p) 126 Ce reaction at 150–200 MeV bombarding energy using multiple particle-gamma coincidence techniques. Measurements were made of gamma-ray angular distributions and production cross sections as a function of energy. The lifetimes of the lowest states in the ground state band of 126 Ce were measured using the recoil distance method. The first excited state was found to have a meanlife of τ m = 949 ± 53 ps, which is consistent with a ground state quadrupole deformation of e 2 = 0.28 ± 0.01 assuming axial symmetry and a uniform charge distribution. In the ground state rotational sequence a backbend is observed at h w c ≏ 0.32 MeV . This appears to be due to the alignment of h 11 2 protons. These properties are compared with the results of potential energy surface and cranked shell model calculations and are assessed in the context of the systematic behaviour of even-even nuclei in this mass region.