Cross section measurement of the 144 Sm ( α , n ) 147 Gd reaction for studying the α -nucleus optical potential at astrophysical energies

Gyürky, György and Mohr, Péter and Angyal, Anikó and Halász, Zoltán and Kiss, Gábor Gyula and Mátyus, Zsolt and Szegedi, Tibor Norbert and Szücs, Tamás and Fülöp, Zsolt (2023) Cross section measurement of the 144 Sm ( α , n ) 147 Gd reaction for studying the α -nucleus optical potential at astrophysical energies. PHYSICAL REVIEW C, 107 (02). ISSN 2469-9985 (print); 2469-9993 (online)

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Abstract

Background: Nuclear reactions involving α particles play an important role in various astrophysical processes such as the γ process of heavy element nucleosynthesis. The poorly known low-energy α-nucleus optical potential is a key parameter to estimate the rates of these reactions. Purpose: The α-nucleus optical potential can be tested by measuring the cross section of α scattering as well as α-induced reactions. Low energy elastic α scattering on Sm144 has recently been measured with high precision. The aim of the present work was to complement that work by measuring the (α,n) cross sections on Sm144 at low energies. The experimental data shall be used to constrain the α-nucleus optical model potential. From this potential the Sm144(α,γ)Gd148 reaction rate can be derived with reduced uncertainties. Method: The Sm144(α,n)Gd147 reaction was studied by bombarding Sm targets with α beams provided by the cyclotron accelerator of Atomki. The cross section was determined using the activation method. The γ radiation following the decay of the Gd147 reaction product was measured with a high-purity germanium (HPGe) detector. The experimental data are analyzed within the statistical model. Results: The cross section was measured in the α-energy range between 13 and 20 MeV in 1 MeV steps, i.e., from close above the (α,n) threshold. The results were compared with statistical model calculations using various approaches and parametrizations for the α-nucleus optical potential, and excellent agreement was obtained for two recent potentials. However, these potentials cannot reproduce literature data for the Sm144(α,γ)Gd148 reaction with the same accuracy. Conclusions: Constraints for the α-nucleus potential were derived from an analysis of the new Sm144(α,n)Gd147 data and literature data for Sm144(α,γ)Gd148. These constraints enable a determination of the reaction rate of the Sm144(α,γ)Gd148 reaction with significantly reduced uncertainties of less than a factor of 2.

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