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Open Access Publications from the University of California

Neutron single-particle strengths at N=40, 42: Neutron knockout from Ni 68,70 ground and isomeric states

  • Author(s): Recchia, F
  • Weisshaar, D
  • Gade, A
  • Tostevin, JA
  • Janssens, RVF
  • Albers, M
  • Bader, VM
  • Baugher, T
  • Bazin, D
  • Berryman, JS
  • Brown, BA
  • Campbell, CM
  • Carpenter, MP
  • Chen, J
  • Chiara, CJ
  • Crawford, HL
  • Hoffman, CR
  • Kondev, FG
  • Korichi, A
  • Langer, C
  • Lauritsen, T
  • Liddick, SN
  • Lunderberg, E
  • Noji, S
  • Prokop, C
  • Stroberg, SR
  • Suchyta, S
  • Wimmer, K
  • Zhu, S
  • et al.

The distribution of single-particle strength in Ni67,69 was characterized with one-neutron knockout reactions from intermediate-energy Ni68,70 secondary beams, selectively populating neutron-hole configurations at N=39 and 41, respectively. The spectroscopic strengths deduced from the measured partial cross sections to the individual final states, as tagged by their γ-ray decays, are used to identify and quantify neutron configurations in the wave functions. While Ni69 compares well with shell-model predictions, the results for Ni67 challenge the validity of current effective shell-model Hamiltonians by revealing discrepancies that cannot be explained so far. These results suggest that our understanding of the low-lying states in the neutron-rich, semimagic Ni isotopes may be incomplete and requires further investigation on both the experimental and theoretical sides.

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