Cross-section measurement of the 130Ba(p,γ) 131La reaction for γ-process nucleosynthesis

Netterdon, L. and Endres, A. and Kiss, Gábor Gyula and Mayer, J. and Rauscher, T. and Scholz, P. and Sonnabend, K. and Török, Zsófia and Zilges, A. (2014) Cross-section measurement of the 130Ba(p,γ) 131La reaction for γ-process nucleosynthesis. PHYSICAL REVIEW C, 90 (3). ISSN 2469-9985

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Abstract

Background: Deviations between experimental data of charged-particle induced reactions and calculations within the statistical model are frequently found. An extended data base is needed to address the uncertainties regarding the nuclear-physics input parameters in order to understand the nucleosynthesis of the neutron-deficient p nuclei. Purpose: A measurement of total cross-section values of the 130Ba(p,γ) 131La reaction at low proton energies allows a stringent test of statistical model predictions with different proton+nucleus optical model potentials. Since no experimental data are available for proton-capture reactions in this mass region around A ≈ 130, this measurement can be an important input to test the global applicability of proton+nucleus optical model potentials. Method: The total reaction cross-section values were measured by means of the activation method. After the irradiation with protons, the reaction yield was determined by use of γ-ray spectroscopy using two clover-type high-purity germanium detectors. In total, cross-section values for eight different proton energies could be determined in the energy range between 3.6 MeV ≤ Ep ≤ 5.0 MeV, thus, inside the astrophysically relevant energy region. Results: The measured cross-section values were compared to Hauser-Feshbach calculations using the statistical model codes TALYS and SMARAGD with different proton+nucleus optical model potentials. With the semi-microscopic JLM proton+nucleus optical model potential used in the SMARAGD code, the absolute cross-section values are reproduced well, but the energy dependence is too steep at the lowest energies. The best description is given by a TALYS calculation using the semi-microscopic Bauge proton+nucleus optical model potential using a constant renormalization factor. Conclusions: The statistical model calculation using the Bauge semi-microscopic proton+nucleus optical model potential deviates by a constant factor of 2.1 from the experimental data. Using this model, an experimentally supported stellar reaction rate for proton capture on the p nucleus 130Ba was calculated. At astrophysical temperatures, an increase in the stellar reaction rate of 68 % compared to rates obtained from the widely used NON-SMOKER code is found. This measurement extends the scarce experimental data base for charged-particle induced reactions, which can be helpful to derive a more globally applicable proton+nucleus optical model potential.

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