Year: 2018
Type: article
Abstract: Background: $\ensuremath{\alpha}$-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 $\ensuremath{\alpha}$+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 $\ensuremath{\alpha}$-capture and the $\ensuremath{\alpha}$-induced reaction cross sections on the nucleus $^{115}\mathrm{In}$ 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 $\ensuremath{\alpha}$+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 $\ensuremath{\gamma}$ rays and characteristic x rays emitted during the electron capture decay of the produced Sb isotopes. The $^{115}\mathrm{In}(\ensuremath{\alpha},\ensuremath{\gamma})^{119}\mathrm{Sb}$ and $^{115}\mathrm{In}(\ensuremath{\alpha},n)\phantom{\rule{0.16em}{0ex}}^{118}\mathrm{Sb}^{m}$ reaction cross sections were measured between ${E}_{\mathrm{c}.\mathrm{m}.}=8.83$ and 15.58 MeV, and the $^{115}\mathrm{In}(\ensuremath{\alpha},n)\phantom{\rule{0.16em}{0ex}}^{118}\mathrm{Sb}^{g}$ reaction was studied between ${E}_{\mathrm{c}.\mathrm{m}.}=11.10$ and 15.58 MeV. The theoretical analysis was performed within the statistical model.Results: The simultaneous measurement of the ($\ensuremath{\alpha},\ensuremath{\gamma}$) and ($\ensuremath{\alpha},n$) cross sections allowed us to determine a best-fit combination of all parameters for the statistical model. The $\ensuremath{\alpha}$+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 $\ensuremath{\gamma}$-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 ($\ensuremath{\alpha},\ensuremath{\gamma}$) cross section of $^{115}\mathrm{In}$ to the astrophysical Gamow window with reasonable uncertainties. However, still further improvements of the $\ensuremath{\alpha}$-nucleus potential are required for a global description of elastic ($\ensuremath{\alpha},\ensuremath{\alpha}$) scattering and $\ensuremath{\alpha}$-induced reactions in a wide range of masses and energies.
Source: Physical Review C
Language: Latvian
Subfield: Nuclear and High Energy Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: hybrid
OpenAlex ID: W2803471084