Recent theoretical developments in nuclear charge-exchange reactions

Abstract

The (p, n) and (n, p) charge-exchange reactions are a suitable tool in nuclear-structure studies. At intermediate energies, the interaction with the target resembles that between free nucleons, which makes the probes mostly susceptible to the spin dynamics of the nucleus. We review the current theoretical picture of nucleon–nucleus charge-exchange reactions. A brief introduction to the theory of direct reactions in the impulse approximation is given. We then discuss the random-phase approximation (RPA) linear response theory, which is widely used in the calculation of cross sections and related observables. To understand correctly the shape of the continuum cross sections, one needs a more sophisticated theory. We discuss suitable extensions of the RPA that incorporate spreading effects as well as escape effects. Charge-exchange reactions of the (n, p) type have important implications for the evolution of massive stars. The relevance for Type-II supernovae is discussed.