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Experimentally constrained (p,γ)Y89 and (n,γ)Y89 reaction rates relevant to p-process nucleosynthesis

A. C. Larsen, M. Guttormsen, R. Schwengner, D. L. Bleuel, S. Goriely, S. Harissopulos, F. L. Bello Garrote, Y. Byun, T. K. Eriksen, F. Giacoppo, A. Görgen, T. W. Hagen, M. Klintefjord, T. Renstrøm, S. J. Rose, E. Sahin, S. Siem, T. G. Tornyi, G. M. Tveten, A. V. Voinov, and M. Wiedeking
Phys. Rev. C 93, 045810 – Published 21 April 2016
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  • INTRODUCTION
  • EXPERIMENTAL DETAILS AND EXTRACTION OF…
  • SHELL-MODEL CALCULATIONS AND MODELS FOR…
  • CROSS SECTION AND RATE CALCULATIONS
  • SUMMARY AND OUTLOOK
  • ACKNOWLEDGMENTS
    • References

    Abstract

    The nuclear level density and the γ-ray strength function have been extracted for Y89 by using the Oslo method on Y89(p,p′γ)Y89 coincidence data. The γ-ray strength function displays a low-energy enhancement consistent with previous observations in this mass region (Mo93–98). Shell-model calculations support the conclusion that the observed enhancement is due to strong, low-energy M1 transitions at high excitation energies. The data were further used as input for calculations of the Sr88(p,γ)Y89 and Y88(n,γ)Y89 cross sections with the talys reaction code. Comparison with cross-section data, where available, as well as with values from the BRUSLIB library, shows a satisfying agreement.

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    • Received 4 October 2015
    • Revised 2 March 2016

    DOI:https://doi.org/10.1103/PhysRevC.93.045810

    ©2016 American Physical Society

    Physics Subject Headings (PhySH)

    1. Research Areas
    Energy levelsH & He induced nuclear reactionsNucleosynthesis in explosive environments
    1. Properties
    59 ≤ A ≤ 8990 ≤ A ≤ 149
    Nuclear Physics

    Authors & Affiliations

    A. C. Larsen1,*, M. Guttormsen1,†, R. Schwengner2,‡, D. L. Bleuel3, S. Goriely4, S. Harissopulos5, F. L. Bello Garrote1, Y. Byun6, T. K. Eriksen1, F. Giacoppo1, A. Görgen1, T. W. Hagen1, M. Klintefjord1, T. Renstrøm1, S. J. Rose1, E. Sahin1, S. Siem1, T. G. Tornyi1, G. M. Tveten1, A. V. Voinov6, and M. Wiedeking7

    • 1Department of Physics, University of Oslo, N-0316 Oslo, Norway
    • 2Helmholtz-Zentrum Dresden-Rossendorf, 01328 Dresden, Germany
    • 3Lawrence Livermore National Laboratory, Livermore, California 94551, USA
    • 4Institut d'Astronomie et d'Astrophysique, Universite Libre de Bruxelles, Brussels, Belgium
    • 5Institute of Nuclear and Particle Physics, NCSR “Demokritos”, Athens, Greece
    • 6Department of Physics and Astronomy, Ohio University, Athens, Ohio 45701, USA
    • 7iThemba LABS, P.O. Box 722, 7129 Somerset West, South Africa

    • *a.c.larsen@fys.uio.no
    • †magne.guttormsen@fys.uio.no
    • ‡r.schwengner@hzdr.de

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    Vol. 93, Iss. 4 — April 2016

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    Images

    • Figure 1
      Figure 1

      ΔE−E plot for Y89+p (a), with the deposited energy in the thick E detector versus the thin ΔE detector for θ=132∘±1∘, and (b) the sum of the deposited energy in the thin and thick detector for the same angle. The labeled peaks are the ground state (0), the first excited 909 keV level (1), the second excited 1507 keV level (2), and the third excited 1744 keV level (3).

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    • Figure 2
      Figure 2

      (a) Raw NaI spectra and (b) unfolded, primary γ spectra for each initial excitation-energy bin for Y89(p,p′γ)Y89; the area within the dashed lines are used in the further analysis, i.e., the data for Eγ>2.00 MeV, 5.43<Ex<10.98 MeV are selected. (c) Projection of the primary γ spectra for the range of excitation energies between the lines.

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    • Figure 3
      Figure 3

      Spin distributions for Y89 at the neutron-separation energy Sn=11.482 MeV for the three different normalization approaches. For FG09 and FG05, Eq. (6) is used with their respective spin-cutoff parameters in Eqs. (4) and (5). The HFB+c calculations assume no specific shape of the spin distribution but happens to be very similar to FG05 in this case.

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    • Figure 4
      Figure 4

      Level densities at Sn in the Y mass region with global systematics of (a), (b) Ref. [26] (FG05) and (c), (d) Ref. [27] (FG09) (see Table 1). The unknown level density for Y89 is shown as a purple diamond. The global-systematics predictions are scaled with a factor of 0.31 and 0.34 for the FG05 and FG09 approaches, respectively. The error bands show the upper-limit scaling of (a), (b) 0.40 for FG05 and (c), (d) the lower limit of 0.27 for FG09.

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    • Figure 5
      Figure 5

      The extracted level density of Y89. The black points give the HFB+c normalization, the lower and upper limits are shown as azure lines. The inset shows a zoom of the high-Ex part.

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    • Figure 6
      Figure 6

      Normalized γSF of Y89 compared to Y89(γ,n)+Y89(γ,np) data from Refs. [36, 37], and evaluated data from Ref. [38]. The black points are obtained with the HFB+c normalization, and the azure lines show the lower and upper limits.

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    • Figure 7
      Figure 7

      The γSF of Y89 together with photonuclear data [36, 37] and evaluated (γ,n) data from Ref. [38] compared with models for the dipole strength.

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    • Figure 8
      Figure 8

      Same as Fig. 7 but with the QRPA E1 strength (see text).

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    • Figure 9
      Figure 9

      (a) Input γSFs of Y89, note that the talys default is for En=1 MeV, corresponding to an initial excitation energy of 12.48 MeV in the GLo model, and that the GLo model is by default normalized to a radiative width 〈Γγ〉=170 meV taken from an interpolation routine in talys; (b) the resulting Y88(n,γ)Y89 cross sections, (c) and the corresponding astrophysical reaction rates compared to the BRUSLIB (dashed magenta line, Ref. [50]) and the JINA REACLIB (green solid line, Ref. [53]). The minimum and maximum predictions from the models implemented in talys are also shown (thick, black lines).

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    • Figure 10
      Figure 10

      (a) Calculated Sr88(p,γ)Y89 cross sections shown as a blue-shaded band compared to data from Ref. [61], and (b) the corresponding astrophysical reaction rates compared to the BRUSLIB (dashed magenta line, Ref. [50]) and the JINA REACLIB (green solid line, Ref. [53]). The minimum and maximum predictions from the models implemented in talys are also shown (thick, black lines), as well as the result using default input parameters (black crosses).

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