The Path to Improved Reaction Rates for Astrophysics

Abstract

This review focuses on nuclear reactions in astrophysics and, more specifically, on reactions with light ions (nucleons and α particles) proceeding via the strong interaction. It is intended to present the basic definitions essential for studies in nuclear astrophysics, to point out the differences between nuclear reactions taking place in stars and in a terrestrial laboratory, and to illustrate some of the challenges to be faced in theoretical and experimental studies of those reactions. The discussion revolves around the relevant quantities for astrophysics, which are the astrophysical reaction rates. The sensitivity of the reaction rates to the uncertainties in the prediction of various nuclear properties is explored and some guidelines for experimentalists are also provided.Caminante, son tus huellas el camino, y nada más; Caminante, no hay camino, se hace camino al andar.Al andar se hace camino y al volver la vista atrás se ve la senda que nunca se ha de volver de pisar. Caminante, no hay camino sino estelas en la mar.

High precision113In(α,α)113In elastic scattering at energies near the Coulomb barrie

“…This indicates a deficiency in the description of either the γ or the neutron transmission (or both) because σ (α,γ ) is proportional to T γ /T n at these energies. This ratio depends on the nuclear input used, such as the optical potential and discrete final states for T n and the gamma/strength function and level density for T γ [56,66].…”

Experimental study of the astrophysicalγ-process reactionXe124(α,γ)BaHalász1, Somorjai2, Gyürky3 et al. 2016Phys. Rev. C160170View full textAdd to dashboardCite

“…The results of statistical model calculations for the cross sections obtained with the default settings of the Hauser-Feshbach codes NON-SMOKER [50,51], TALYS [52], and SMARAGD (version 0.9.3s) [53] are also included in the figures. Apart from differences in the internal numerics, the codes mainly differ in the input used to determine the transmission coefficients which are the central quantities in the Hauser-Fesbach approach [54,55]. Of special relevance here is the optical α+nucleus potential, as discussed in more detail below.…”

“…Central to the Hauser-Feshbach model are the averaged widths, computed from transmission coefficients which, in turn, are obtained from solutions of the Schrödinger equation using effective inter- action potentials or, for photon transmission coefficients, from the knowledge of photon strength functions and nuclear level densities [55]. For reactions in astrophysics, mostly averaged neutron-, proton-, α-, and γ widths have to be considered.…”

Statistical Model Calculations for (n,γ) Reactions

“…There are several, well-established HF code packages for cross section and reaction rate calculation available on the market including TALYS, NON-SMOKER, EM-PIRE [16], MOST [17] and SMARAGD [18]. In each case the code package requires a user to select between the various available options for nuclear input model.…”