Low-spin states in the neutron-rich, $N=90$ nuclide ${}^{146}\mathrm{Ba}$ were populated following $\beta$ decay of ${}^{146}\mathrm{Cs}$, with the goal of clarifying the development of deformation in barium isotopes through delineation of their nonyrast structures. Fission fragments of ${}^{146}\mathrm{Cs}$ were extracted from a 1.7-Ci ${}^{252}\mathrm{Cf}$ source and mass selected using the CAlifornium Rare Ion Breeder Upgrade (CARIBU) facility. Low-energy ions were deposited at the center of a box of thin $\beta$ detectors, surrounded by a highly efficient high-purity Ge array. The new ${}^{146}\mathrm{Ba}$ decay scheme now contains 31 excited levels extending up to $\sim 2.5$ MeV excitation energy, double what was previously known. These data are compared to predictions from the interacting boson approximation (IBA) model. It appears that the abrupt shape change found at $N=90$ in Sm and Gd is much more gradual in Ba and Ce, due to an enhanced role of the $\gamma$ degree of freedom.

• Received 19 November 2015

DOI:https://doi.org/10.1103/PhysRevC.93.014306