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

Abstract

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:
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)
OSTI Identifier:
1346844
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
Resource Type:
Journal Article: 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)
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; atomic and nuclear physics

Citation Formats

Spyrou, A., Liddick, S. N., Naqvi, F., Crider, B. P., Dombos, A. C., Bleuel, D. L., Brown, B. A., Couture, Aaron Joseph, Campo, L. Crespo, Guttormsen, M., Larsen, A. C., Lewis, R., Moller, Peter, Mosby, Shea Morgan, Mumpower, Matthew Ryan, Perdikakis, G., Prokop, C. J., Renstrom, T., Siem, S., Quinn, S. J., and Valenta, S.. Strong neutron-γ competition above the neutron threshold in the decay of Co70. United States: N. p., 2016. Web. doi:10.1103/PhysRevLett.117.142701.
Spyrou, A., Liddick, S. N., Naqvi, F., Crider, B. P., Dombos, A. C., Bleuel, D. L., Brown, B. A., Couture, Aaron Joseph, Campo, L. Crespo, Guttormsen, M., Larsen, A. C., Lewis, R., Moller, Peter, Mosby, Shea Morgan, Mumpower, Matthew Ryan, Perdikakis, G., Prokop, C. J., Renstrom, T., Siem, S., Quinn, S. J., & Valenta, S.. Strong neutron-γ competition above the neutron threshold in the decay of Co70. United States. doi:10.1103/PhysRevLett.117.142701.
Spyrou, A., Liddick, S. N., Naqvi, F., Crider, B. P., Dombos, A. C., Bleuel, D. L., Brown, B. A., Couture, Aaron Joseph, Campo, L. Crespo, Guttormsen, M., Larsen, A. C., Lewis, R., Moller, Peter, Mosby, Shea Morgan, Mumpower, Matthew Ryan, Perdikakis, G., Prokop, C. J., Renstrom, T., Siem, S., Quinn, S. J., and Valenta, S.. 2016. "Strong neutron-γ competition above the neutron threshold in the decay of Co70". United States. doi:10.1103/PhysRevLett.117.142701. https://www.osti.gov/servlets/purl/1346844.
@article{osti_1346844,
title = {Strong neutron-γ competition above the neutron threshold in the decay of Co70},
author = {Spyrou, A. and Liddick, S. N. and Naqvi, F. and Crider, B. P. and Dombos, A. C. and Bleuel, D. L. and Brown, B. A. and Couture, Aaron Joseph and Campo, L. Crespo and Guttormsen, M. and Larsen, A. C. and Lewis, R. and Moller, Peter and Mosby, Shea Morgan and Mumpower, Matthew Ryan and Perdikakis, G. and Prokop, C. J. and Renstrom, T. and Siem, S. and Quinn, S. J. and Valenta, S.},
abstractNote = {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.},
doi = {10.1103/PhysRevLett.117.142701},
journal = {Physical Review Letters},
number = 14,
volume = 117,
place = {United States},
year = 2016,
month = 9
}

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  • The β -decay intensity of 70 Co 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 approximationmore » (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. 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.« less
  • The β-decay half-lives of 94 neutron-rich nuclei 144 $-$ 151Cs, 146 $-$ 154Ba, 148 $-$ 156La, 1 50 $-$ 158Ce, 153 $-$160Pr, 156 $-$ 162 Nd, 159 $-$ 163Pm, 160 $-$ 166Sm, 161 $-$ 168Eu , 165 $-$ 170Gd, 166 $-$ 172Tb, 169 $-$ 173Dy, 172 $-$ 175Ho, and two isomeric states 174 mEr, 172 mDy were measured at the Radioactive Isotope Beam Factory, providing a new experimental basis to test theoretical models. Strikingly large drops of β -decay half-lives are observed at neutron-number N = 97 for 58Ce, 59Pr, 60Nd , and 62Sm, and N = 105 for 63Eu,more » 64Gd, 65Tb, and 66Dy. Features in the data mirror the interplay between pairing effects and microscopic structure. In conclusion, $r$-process network calculations performed for a range of mass models and astrophysical conditions show that the 57 half-lives measured for the first time play an important role in shaping the abundance pattern of rare-earth elements in the solar system.« less
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