Gy. Gyürky, P. Mohr, A. Angyal, Z. Halász, G.G. Kiss, Zs. Mátyus, T.N. Szegedi, T. Szücs, Zs. Fülöp:
Cross section measurement of the ¹⁴⁴Sm(α,n)¹⁴⁷Gd reaction for studying the α-nucleus optical potential at astrophysical energies
Physical Review C 107 (2023) 025803

DOI: https://doi.org/10.1103/PhysRevC.107.025803

Published: 8 February 2023

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 αscattering as well as α-induced reactions. Low energy elastic α scattering on ¹⁴⁴Sm 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 ¹⁴⁴Sm at low energies. The experimental data shall be used to constrain the α-nucleus optical model potential. From this potential the ¹⁴⁴Sm(α,γ)¹⁴⁸Gd reaction rate can be derived with reduced uncertainties.

Method: The ¹⁴⁴Sm(α,n)¹⁴⁷Gd 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 147Gd 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 ¹⁴⁴Sm(α,γ)¹⁴⁸Gd reaction with the same accuracy.

Conclusions: Constraints for the α-nucleus potential were derived from an analysis of the new ¹⁴⁴Sm(α,n)¹⁴⁷Gd data and literature data for ¹⁴⁴Sm(α,γ)¹⁴⁸Gd. These constraints enable a determination of the reaction rate of the ¹⁴⁴Sm(α,γ)¹⁴⁸Gd reaction with significantly reduced uncertainties of less than a factor of 2.