Isotopic dependence of (n,α) reaction cross sections for Fe and Sn nuclei

Abstract

The $(n,\alpha )$ reactions play an important role for the energy generation and the synthesis of chemical elements in the stars, as well as for nuclear engineering and medical applications. The aim of this study is to explore the evolution of $(n,\alpha )$ reactions in Fe and Sn isotope chains in order to assess the cross section properties with the increase of neutron number in target nucleus, and to make a comparison with other relevant neutron induced reactions. The cross section calculations are based on the statistical Hauser-Feshbach and exciton models in TALYS nuclear reaction code, using global optical model potential that is additionally adjusted by the $(n,\alpha )$ cross section data for ⁵⁴Fe and ¹¹⁸Sn. The calculations of $(n,\alpha )$ reactions in Fe and Sn isotopes provide the insight into their isotopic dependence and properties over the complete relevant range of neutron energies. The cross sections result in pronounced maxima at lower-mass isotopes, and rather strong decrease for neutron-rich nuclei consistent with the reduction of the reaction Q-value and increased contributions from other exit channels from compound nucleus. The analysis of the Maxwellian averaged cross sections at temperatures in stellar environment shows that the $(n,\alpha )$ reactions have significant contributions for low-mass Fe isotopes, that is opposite than for Sn isotopes. For both neutron rich isotopes γ and neutron emissions dominate, with their interplay depending on the temperature involved.