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γ -soft Ba 146 and the role of nonaxial shapes at N≈90

  • Author(s): Mitchell, AJ
  • Lister, CJ
  • McCutchan, EA
  • Albers, M
  • Ayangeakaa, AD
  • Bertone, PF
  • Carpenter, MP
  • Chiara, CJ
  • Chowdhury, P
  • Clark, JA
  • Copp, P
  • David, HM
  • Deo, AY
  • DiGiovine, B
  • D'Olympia, N
  • Dungan, R
  • Harding, RD
  • Harker, J
  • Hota, SS
  • Janssens, RVF
  • Kondev, FG
  • Liu, SH
  • Ramayya, AV
  • Rissanen, J
  • Savard, G
  • Seweryniak, D
  • Shearman, R
  • Sonzogni, AA
  • Tabor, SL
  • Walters, WB
  • Wang, E
  • Zhu, S
  • et al.
Abstract

© 2016 American Physical Society. 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.

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