Background: α-nucleus optical potentials are basic ingredients of statistical model calculations used in nucleosynthesis simulations. While the nucleon+nucleus optical potential is fairly well known, for the α+nucleus optical potential several different parameter sets exist and large deviations, reaching sometimes even an order of magnitude, are found between the cross section predictions calculated using different parameter sets. Purpose: A measurement of the radiative α-capture and the α-induced reaction cross sections on the nucleus In115 at low energies allows a stringent test of statistical model predictions. Since experimental data are scarce in this mass region, this measurement can be an important input to test the global applicability of α+nucleus optical model potentials and further ingredients of the statistical model. Methods: The reaction cross sections were measured by means of the activation method. The produced activities were determined by off-line detection of the γ rays and characteristic x rays emitted during the electron capture decay of the produced Sb isotopes. The In115(α,γ)Sb119 and In115(α,n)Sbm118 reaction cross sections were measured between Ec.m.=8.83 and 15.58 MeV, and the In115(α,n)Sbg118 reaction was studied between Ec.m.=11.10 and 15.58 MeV. The theoretical analysis was performed within the statistical model. Results: The simultaneous measurement of the (α,γ) and (α,n) cross sections allowed us to determine a best-fit combination of all parameters for the statistical model. The α+nucleus optical potential is identified as the most important input for the statistical model. The best fit is obtained for the new Atomki-V1 potential, and good reproduction of the experimental data is also achieved for the first version of the Demetriou potentials and the simple McFadden-Satchler potential. The nucleon optical potential, the γ-ray strength function, and the level density parametrization are also constrained by the data although there is no unique best-fit combination. Conclusions: The best-fit calculations allow us to extrapolate the low-energy (α,γ) cross section of In115 to the astrophysical Gamow window with reasonable uncertainties. However, still further improvements of the α-nucleus potential are required for a global description of elastic (α,α) scattering and α-induced reactions in a wide range of masses and energies.
ASJC Scopus subject areas
- Nuclear and High Energy Physics