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Title: Strong neutron- γ competition above the neutron threshold in the decay of Co 70

The β-decay intensity of 70Co was measured for the first time using the technique of total absorption spectroscopy. The large β-decay Q value [12.3(3) MeV] offers a rare opportunity to study β-decay properties in a broad energy range. Two surprising features were observed in the experimental results, namely, the large fragmentation of the β intensity at high energies, as well as the strong competition between γ rays and neutrons, up to more than 2 MeV above the neutron-separation energy. The data are compared to two theoretical calculations: the shell model and the quasiparticle random phase approximation (QRPA). Both models seem to be missing a significant strength at high excitation energies. Possible interpretations of this discrepancy are discussed. The shell model is used for a detailed nuclear structure interpretation and helps to explain the observed γ-neutron competition. The comparison to the QRPA calculations is done as a means to test a model that provides global β-decay properties for astrophysical calculations. Our work demonstrates the importance of performing detailed comparisons to experimental results, beyond the simple half-life comparisons. Finally, a realistic and robust description of the β-decay intensity is crucial for our understanding of nuclear structure as well as of r-process nucleosynthesis.
Authors:
 [1] ;  [1] ;  [1] ;  [1] ;  [1] ;  [2] ;  [1] ; ORCiD logo [3] ;  [4] ;  [4] ;  [4] ;  [1] ; ORCiD logo [3] ; ORCiD logo [3] ; ORCiD logo [3] ;  [5] ;  [1] ;  [4] ;  [4] ;  [1] more »;  [6] « less
  1. Michigan State Univ., East Lansing, MI (United States)
  2. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  3. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  4. Univ. of Oslo, Oslo (Norway)
  5. Central Michigan Univ., Mount Pleasant, MI (United States); Michigan State Univ., East Lansing, MI (United States)
  6. Charles Univ. in Prague (Czech Republic)
Publication Date:
Report Number(s):
LA-UR-16-26924; LLNL-JRNL-737170
Journal ID: ISSN 0031-9007; PRLTAO; TRN: US1701599
Grant/Contract Number:
AC52-06NA25396; AC52-07NA27344
Type:
Accepted Manuscript
Journal Name:
Physical Review Letters
Additional Journal Information:
Journal Volume: 117; Journal Issue: 14; Journal ID: ISSN 0031-9007
Publisher:
American Physical Society (APS)
Research Org:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org:
USDOE National Nuclear Security Administration (NNSA)
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; atomic and nuclear physics
OSTI Identifier:
1346844
Alternate Identifier(s):
OSTI ID: 1378498