γ -soft Ba 146 and the role of nonaxial shapes at N ≈ 90
/ Authors
A. Mitchell, C. Lister, E. McCutchan, M. Albers, A. D. Ayangeakaa, P. Bertone, M. Carpenter, C. Chiara, P. Chowdhury, J. Clark
and 22 more authors
P. Copp, H. David, A. Deo, B. DiGiovine, N. D'Olympia, R. Dungan, R. Harding, J. Harker, S. Hota, R. Janssens, F. Kondev, S. Liu, A. Ramayya, J. Rissanen, G. Savard, D. Seweryniak, R. Shearman, A. Sonzogni, S. Tabor, W. Walters, E. Wang, S. Zhu
/ Abstract
Low-spin states in the neutron-rich, N=90 nuclide Ba146 were populated following β decay of Cs146, with the goal of clarifying the development of deformation in barium isotopes through delineation of their nonyrast structures. Fission fragments of Cs146 were extracted from a 1.7-Ci Cf252 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 β detectors, surrounded by a highly efficient high-purity Ge array. The new Ba146 decay scheme now contains 31 excited levels extending up to ~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 γ degree of freedom.
Journal: Physical Review C