- 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.
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.