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Direct Evidence of Octupole Deformation in Neutron-Rich ^{144}Ba.

  • Author(s): Bucher, B
  • Zhu, S
  • Wu, CY
  • Janssens, RVF
  • Cline, D
  • Hayes, AB
  • Albers, M
  • Ayangeakaa, AD
  • Butler, PA
  • Campbell, CM
  • Carpenter, MP
  • Chiara, CJ
  • Clark, JA
  • Crawford, HL
  • Cromaz, M
  • David, HM
  • Dickerson, C
  • Gregor, ET
  • Harker, J
  • Hoffman, CR
  • Kay, BP
  • Kondev, FG
  • Korichi, A
  • Lauritsen, T
  • Macchiavelli, AO
  • Pardo, RC
  • Richard, A
  • Riley, MA
  • Savard, G
  • Scheck, M
  • Seweryniak, D
  • Smith, MK
  • Vondrasek, R
  • Wiens, A
  • et al.
Abstract

The neutron-rich nucleus ^{144}Ba (t_{1/2}=11.5  s) is expected to exhibit some of the strongest octupole correlations among nuclei with mass numbers A less than 200. Until now, indirect evidence for such strong correlations has been inferred from observations such as enhanced E1 transitions and interleaving positive- and negative-parity levels in the ground-state band. In this experiment, the octupole strength was measured directly by sub-barrier, multistep Coulomb excitation of a post-accelerated 650-MeV ^{144}Ba beam on a 1.0-mg/cm^{2} ^{208}Pb target. The measured value of the matrix element, ⟨3_{1}^{-}∥M(E3)∥0_{1}^{+}⟩=0.65(+17/-23) eb^{3/2}, corresponds to a reduced B(E3) transition probability of 48(+25/-34)  W.u. This result represents an unambiguous determination of the octupole collectivity, is larger than any available theoretical prediction, and is consistent with octupole deformation.

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