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Title: Enhanced low-energy γ -decay strength of Ni 70 and its robustness within the shell model

Abstract

Neutron-capture reactions on very neutron-rich nuclei are essential for heavy-element nucleosynthesis through the rapid neutron-capture process, now shown to take place in neutron-star merger events. For these exotic nuclei, radiative neutron capture is extremely sensitive to their γ -emission probability at very low γ energies. In this work, we present measurements of the γ -decay strength of 70Ni over the wide range 1.3 Eγ 8 MeV. A significant enhancement is found in the γ -decay strength for transitions with Eγ < 3 MeV. At present, this is the most neutron-rich nucleus displaying this feature, proving that this phenomenon is not restricted to stable nuclei. We have performed E1-strength calculations within the quasiparticle time-blocking approximation, which describe our data above Eγ 5 MeV very well. Moreover, large-scale shell-model calculations indicate an M1 nature of the low-energy γ strength. This turns out to be remarkably robust with respect to the choice of interaction, truncation, and model space, and we predict its presence in the whole isotopic chain, in particular the neutron-rich 72,74,76Ni.

Authors:
 [1];  [1];  [1];  [1];  [2];  [3];  [4];  [5];  [6];  [7];  [8];  [9];  [1];  [10];  [3];  [2];  [9];  [4];  [11];  [4] more »;  [3];  [1] « less
  1. Univ. of Oslo (Norway). Dept. of Physics
  2. Michigan State Univ., East Lansing, MI (United States). National Superconducting Cyclotron Lab. and Dept. of Chemistry
  3. Michigan State Univ., East Lansing, MI (United States). National Superconducting Cyclotron Lab., Joint Inst. for Nuclear Astrophysics and Dept. of Physics and Astronomy
  4. Michigan State Univ., East Lansing, MI (United States). National Superconducting Cyclotron Lab.
  5. Michigan State Univ., East Lansing, MI (United States). National Superconducting Cyclotron Lab. and Dept. of Physics and Astronomy
  6. Leypunsky Inst. of Physics and Power Engineering (IPPE), Obninsk (Russian Federation)
  7. National Research Centre (NRC), Moscow (Russian Federation). Kurchatov Inst. (NRCKI)
  8. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  9. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  10. Michigan State Univ., East Lansing, MI (United States). National Superconducting Cyclotron Lab.; Mississippi State Univ., Mississippi State, MS (United States). Dept. of Physics and Astronomy
  11. Michigan State Univ., East Lansing, MI (United States). National Superconducting Cyclotron Lab. and Joint Inst. for Nuclear Astrophysics; Central Michigan Univ., Mount Pleasant, MI (United States). Dept. of Physics
Publication Date:
Research Org.:
Michigan State Univ., East Lansing, MI (United States); 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); European Research Council (ERC); European Cooperation in Science and Technology (COST); Research Council of Norway (RCN); U.S.- Norway Fulbright Foundation for Educational Exchange; Russian Science Foundation; Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States); National Science Foundation (NSF)
Contributing Org.:
Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
OSTI Identifier:
1465115
Alternate Identifier(s):
OSTI ID: 1439494; OSTI ID: 1465113; OSTI ID: 1474268; OSTI ID: 1495651; OSTI ID: 1657663
Report Number(s):
LLNL-JRNL-758361
Journal ID: ISSN 2469-9985; PRVCAN; TRN: US1902431
Grant/Contract Number:  
NA0003221; ERC-STG-2014; 637686; 210007; 16-12-10155; AC52- 07NA27344; NA-0003180; NA-0000979; PHY 1102511; PHY 1430152; PHY 1350234; PHY 1404442; AC52-06NA25396; AC52-07NA27344
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Physical Review C
Additional Journal Information:
Journal Volume: 97; Journal Issue: 5; Journal ID: ISSN 2469-9985
Publisher:
American Physical Society (APS)
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; 79 ASTRONOMY AND ASTROPHYSICS; electromagnetic transitions; energy levels and level densities; nuclear astrophysics; nuclear structure and decays; nucleosynthesis in explosive environments; rare and new isotopes; shell model; 59 ≤ A ≤ 89; Physics - Nuclear physics and radiation physics

Citation Formats

Larsen, A. C., Midtbø, J. E., Guttormsen, M., Renstrøm, T., Liddick, S. N., Spyrou, A., Karampagia, S., Brown, B. A., Achakovskiy, O., Kamerdzhiev, S., Bleuel, D. L., Couture, A., Campo, L. Crespo, Crider, B. P., Dombos, A. C., Lewis, R., Mosby, S., Naqvi, F., Perdikakis, G., Prokop, C. J., Quinn, S. J., and Siem, S. Enhanced low-energy γ-decay strength of Ni70 and its robustness within the shell model. United States: N. p., 2018. Web. doi:10.1103/PhysRevC.97.054329.
Larsen, A. C., Midtbø, J. E., Guttormsen, M., Renstrøm, T., Liddick, S. N., Spyrou, A., Karampagia, S., Brown, B. A., Achakovskiy, O., Kamerdzhiev, S., Bleuel, D. L., Couture, A., Campo, L. Crespo, Crider, B. P., Dombos, A. C., Lewis, R., Mosby, S., Naqvi, F., Perdikakis, G., Prokop, C. J., Quinn, S. J., & Siem, S. Enhanced low-energy γ-decay strength of Ni70 and its robustness within the shell model. United States. doi:10.1103/PhysRevC.97.054329.
Larsen, A. C., Midtbø, J. E., Guttormsen, M., Renstrøm, T., Liddick, S. N., Spyrou, A., Karampagia, S., Brown, B. A., Achakovskiy, O., Kamerdzhiev, S., Bleuel, D. L., Couture, A., Campo, L. Crespo, Crider, B. P., Dombos, A. C., Lewis, R., Mosby, S., Naqvi, F., Perdikakis, G., Prokop, C. J., Quinn, S. J., and Siem, S. Wed . "Enhanced low-energy γ-decay strength of Ni70 and its robustness within the shell model". United States. doi:10.1103/PhysRevC.97.054329. https://www.osti.gov/servlets/purl/1465115.
@article{osti_1465115,
title = {Enhanced low-energy γ-decay strength of Ni70 and its robustness within the shell model},
author = {Larsen, A. C. and Midtbø, J. E. and Guttormsen, M. and Renstrøm, T. and Liddick, S. N. and Spyrou, A. and Karampagia, S. and Brown, B. A. and Achakovskiy, O. and Kamerdzhiev, S. and Bleuel, D. L. and Couture, A. and Campo, L. Crespo and Crider, B. P. and Dombos, A. C. and Lewis, R. and Mosby, S. and Naqvi, F. and Perdikakis, G. and Prokop, C. J. and Quinn, S. J. and Siem, S.},
abstractNote = {Neutron-capture reactions on very neutron-rich nuclei are essential for heavy-element nucleosynthesis through the rapid neutron-capture process, now shown to take place in neutron-star merger events. For these exotic nuclei, radiative neutron capture is extremely sensitive to their γ -emission probability at very low γ energies. In this work, we present measurements of the γ -decay strength of 70Ni over the wide range 1.3 Eγ 8 MeV. A significant enhancement is found in the γ -decay strength for transitions with Eγ < 3 MeV. At present, this is the most neutron-rich nucleus displaying this feature, proving that this phenomenon is not restricted to stable nuclei. We have performed E1-strength calculations within the quasiparticle time-blocking approximation, which describe our data above Eγ 5 MeV very well. Moreover, large-scale shell-model calculations indicate an M1 nature of the low-energy γ strength. This turns out to be remarkably robust with respect to the choice of interaction, truncation, and model space, and we predict its presence in the whole isotopic chain, in particular the neutron-rich 72,74,76Ni.},
doi = {10.1103/PhysRevC.97.054329},
journal = {Physical Review C},
issn = {2469-9985},
number = 5,
volume = 97,
place = {United States},
year = {2018},
month = {5}
}

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Cited by: 5 works
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Figures / Tables:

FIG. 1 FIG. 1: (a) 70Ni raw γ spectra versus Ex ; (b) unfolded γ spectra corrected for the SuN response functions for both Eγ and Ex ; (c) distribution of primary γ rays for each Ex bin. The dashed lines show the region used for the analysis. The pixels are 200more » keV wide.« less

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