Cross section of alpha-induced reactions on Au-197 at sub-Coulomb energies

Szücs, Tamás and Mohr, Péter and Gyürky, György and Halász, Zoltán and Huszánk, Róbert and Kiss, Gábor Gyula and Szegedi, Tibor Norbert and Török, Zsófia and Fülöp, Zsolt (2019) Cross section of alpha-induced reactions on Au-197 at sub-Coulomb energies. PHYSICAL REVIEW C, 100 (6). ISSN 2469-9985

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Abstract

Background: Statistical model calculations have to be used for the determination of reaction rates in large-scale reaction networks for heavy-element nucleosynthesis. A basic ingredient of such a calculation is the alpha-nucleus optical model potential. Several different parameter sets are available in literature, but their predictions of alpha-induced reaction rates vary widely, sometimes even exceeding one order of magnitude.Purpose: This paper presents the result of alpha-induced reaction cross-section measurements on gold which could be carried out very close to the astrophysically relevant energy region. The new experimental data are used to test statistical model predictions and to constrain the alpha-nucleus optical model potential.Method: For the measurements, the activation technique was used. The cross section of the (alpha, n) and (alpha, 2n) reactions was determined from gamma-ray counting, while that of the radiative capture was determined via x-ray counting.Results: The cross section of the reactions was measured below E-alpha = 20.0 MeV. In the case of the Au-197(alpha, 2n)Tl-199 reaction down to 17.5 MeV with 0.5-MeV steps, reaching closer to the reaction threshold than ever before. The cross section of Au-197(alpha, n)Tl-200 and Au-197(alpha, gamma)Tl-201 was measured down to E-alpha = 13.6 and 14.0 MeV, respectively, with 0.5-MeV steps above the (alpha, 2n) reaction threshold and with 1.0-MeV steps below that.Conclusions: The new data set is in agreement with the available values from the literature, but is more precise and extends toward lower energies. Cross sections two orders of magnitude lower than those in previous experiments which used gamma-ray counting only were successfully measured, thus providing experimental data at lower energies than ever before. The new precision dataset allows us to find the best-fit alpha-nucleus optical model potential and to predict cross sections in the Gamow window with smaller uncertainties.

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