Using indirect methods to explore low-energy fusion cross sections in nuclear astrophysics

Abstract

Nuclear reactions within stellar environments typically manifest at energies well below 1 MeV. As a consequence, the Coulomb barrier strongly suppresses the cross section, diminishing it to values as minute as a few nanobarns for charged particles. This challenge in obtaining precise input data for astrophysics has prompted the utilization of indirect methodologies. Specifically, approaches such as ANC and THM have been employed to ascertain cross sections for reactions involving photons and charged particles in the exit channel, respectively, obviating the necessity for extrapolation. The discourse explores recent findings arising from the application of these methodologies. For example, the measurement of 6Li(3He,d)7Be is employed to infer the ANC’s of the 3He+4He→ 7Be and p+6Li→ 7Be channels, along with their corresponding radiative-capture cross sections. Furthermore, the THM measurement of the 27Al(p, α)24Mg cross section via the 2H(27Al,α 24Mg)n reaction is emphasized. In both instances, the cross section at astrophysical energies has been ascertained with unparalleled precision.