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γ-ray strength function for barium isotopes

H. Utsunomiya, T. Renstrøm, G. M. Tveten, S. Goriely, T. Ari-izumi, V. W. Ingeberg, B. V. Kheswa, Y.-W. Lui, S. Miyamoto, S. Hilaire, S. Péru, and A. J. Koning
Phys. Rev. C 100, 034605 – Published 4 September 2019
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  • INTRODUCTION
  • EXPERIMENTAL PROCEDURE
  • DATA ANALYSIS
  • DISCUSSION
  • CONCLUSION
  • ACKNOWLEDGMENTS
    • References

    Abstract

    Photoneutron cross sections were measured for Ba137 and Ba138 at energies below two-neutron threshold using quasimonochromatic γ-ray beams produced in laser Compton scattering at the NewSUBARU synchrotron radiation facility. The photoneutron data are used to constrain the γ-ray strength function on the basis of the Hartree-Fock-Bogolyubov plus quasiparticle random phase approximation using the Gogny D1M interaction. Supplementing the experimentally constrained γ-ray strength function with the zero-limit E1 and M1 contributions, which are unique to the deexcitation mode, we discuss radiative neutron capture cross sections relevant to the s-process nucleosynthesis of barium isotopes in the vicinity of the neutron magic number 82.

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    • Received 18 June 2019

    DOI:https://doi.org/10.1103/PhysRevC.100.034605

    ©2019 American Physical Society

    Physics Subject Headings (PhySH)

    1. Research Areas
    Electromagnetic transitionsPhotonuclear reactions
    1. Properties
    90 ≤ A ≤ 149
    Nuclear Physics

    Authors & Affiliations

    H. Utsunomiya1,*, T. Renstrøm2, G. M. Tveten2, S. Goriely3, T. Ari-izumi1, V. W. Ingeberg2, B. V. Kheswa2,4, Y.-W. Lui5, S. Miyamoto6, S. Hilaire7, S. Péru7, and A. J. Koning8

    • 1Konan University, Department of Physics, 8-9-1 Okamoto, Higashinada, Kobe 658-8501, Japan
    • 2Department of Physics, University of Oslo, N-0316 Oslo, Norway
    • 3Institut d'Astronomie et d'Astrophysique, Université Libre de Bruxelles, Campus de la Plaine, CP-226, 1050 Brussels, Belgium
    • 4Department of Applied Physics and Engineering Mathematics, University of Johannesburg, Doornfontein, Johannesburg 2028, South Africa
    • 5Cyclotron Institute, Texas A& M University, College Station, Texas 77843, USA
    • 6Laboratory of Advanced Science and Technology for Industry, University of Hyogo, 3-1-2 Kouto, Kamigori, Ako-gun, Hyogo 678-1205, Japan
    • 7CEA, DAM, DIF, F-91297 Arpajon, France
    • 8Nuclear Data Section, International Atomic Energy Agency, A-1400 Vienna, Austria

    • *hiro@konan-u.ac.jp

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    Issue

    Vol. 100, Iss. 3 — September 2019

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    Images

    • Figure 1
      Figure 1

      An excerpt of the chart of nuclei depicting the Ba region along the s-process path.

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    • Figure 2
      Figure 2

      The simulated energy profiles for the γ beams used in the Ba137,138 measurements. The distributions are normalized to unity.

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    • Figure 3
      Figure 3

      Monochromatic cross sections of Ba137 and Ba138. The error bars contain statistical uncertainties from the number of detected neutrons, the uncertainty in the efficiency of the neutron detector and the uncertainly in the pileup method used to determine the number of incoming γ's on target.

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    • Figure 4
      Figure 4

      Unfolded cross sections of Ba137,138 in comparison with the previous measurements for Ba138 [34].

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    • Figure 5
      Figure 5

      (a) Comparison of the D1M+QRPA (solid lines) and SMLO (dotted lines) γSF for Ba137 with the measured strength function extracted from the present NewSUBARU experiment (red circles). The E1 mode is shown by blue lines and M1 by green lines. (b) same for and Ba138γSF. Previous measurements from nuclear resonance fluorescence [32] for the E1 (blue squares) and M1 (green circles) modes, as well as photoneutron data (solid circles) [34] and its evaluation (open diamonds) [35] are also shown.

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    • Figure 6
      Figure 6

      (a) Present Ba137(γ,n)Ba136 measured cross sections compared with the talys calculations based on the SMLO (dashed blue line) and D1M+QRPA (solid red line) γSF. (b) same for Ba138(γ,n)Ba137 reaction where previous measurements (black circles) [34] and evaluation (open diamonds) [35] are also shown.

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    • Figure 7
      Figure 7

      (a) Comparison of the Ba136(n,γ)Ba137 measured cross sections [38, 39, 40] with the talys calculations based on the SMLO (dashed blue line) and D1M+QRPA+0lim (solid red line) γSF. (b) same for Ba137(n,γ)Ba138 cross section [40, 41, 42]. Theoretical uncertainties correspond to the use of different level density models [36, 37].

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    • Figure 8
      Figure 8

      Comparison between experimental (black squares) [43] and theoretical Maxwellian-averaged cross sections at 30 keV predicted by the TALYS code with D1M+QRPA+0lim (red circles) or SMLO (blue diamonds) γSF for the radiative neutron capture on Ba isotopes with A lying between 130 and 138.

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