title: Direct Evidence of Octupole Deformation in Neutron-Rich ^{144}Ba.
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.
authors.affiliation: Lawrence Livermore National Laboratory, Livermore, California 94550, USA.
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authors.affiliation: Argonne National Laboratory, Argonne, Illinois 60439, USA.
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authors.affiliation: Lawrence Livermore National Laboratory, Livermore, California 94550, USA.
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authors.affiliation: Argonne National Laboratory, Argonne, Illinois 60439, USA.
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authors.affiliation: University of Rochester, Rochester, New York 14627, USA.
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authors.affiliation: University of Rochester, Rochester, New York 14627, USA.
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authors.affiliation: Argonne National Laboratory, Argonne, Illinois 60439, USA.
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authors.affiliation: Argonne National Laboratory, Argonne, Illinois 60439, USA.
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authors.affiliation: Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
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authors.affiliation: Argonne National Laboratory, Argonne, Illinois 60439, USA.
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authors.affiliation: Argonne National Laboratory, Argonne, Illinois 60439, USA.|University of Maryland, College Park, Maryland 20742, USA.
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authors.affiliation: Argonne National Laboratory, Argonne, Illinois 60439, USA.
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authors.affiliation: Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
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authors.affiliation: Argonne National Laboratory, Argonne, Illinois 60439, USA.
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authors.affiliation: Argonne National Laboratory, Argonne, Illinois 60439, USA.
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authors.affiliation: University of the West of Scotland, Paisley PA1 2BE, United Kingdom.|SUPA, Scottish Universities Physics Alliance, Glasgow G12 8QQ, United Kingdom.
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authors.affiliation: Argonne National Laboratory, Argonne, Illinois 60439, USA.|University of Maryland, College Park, Maryland 20742, USA.
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authors.affiliation: Argonne National Laboratory, Argonne, Illinois 60439, USA.
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authors.affiliation: Argonne National Laboratory, Argonne, Illinois 60439, USA.
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authors.affiliation: Argonne National Laboratory, Argonne, Illinois 60439, USA.
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authors.affiliation: Argonne National Laboratory, Argonne, Illinois 60439, USA.|CSNSM, IN2P3-CNRS, bâtiment 104-108, F-91405 Orsay Campus, France.
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authors.affiliation: Argonne National Laboratory, Argonne, Illinois 60439, USA.
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authors.affiliation: Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
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authors.affiliation: Argonne National Laboratory, Argonne, Illinois 60439, USA.
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authors.affiliation: Ohio University, Athens, Ohio 45701, USA.
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authors.affiliation: Argonne National Laboratory, Argonne, Illinois 60439, USA.
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authors.affiliation: University of the West of Scotland, Paisley PA1 2BE, United Kingdom.|SUPA, Scottish Universities Physics Alliance, Glasgow G12 8QQ, United Kingdom.
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authors.affiliation: Argonne National Laboratory, Argonne, Illinois 60439, USA.
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authors.affiliation: Argonne National Laboratory, Argonne, Illinois 60439, USA.
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