Coupled-Channel Calculations of the Energy Dependence of the (p,n) Charge-Exchange Reaction

Excitation functions of the ($p,n\tilde{p}$) reaction on ${}_{}{}^{91}{}_{}{}^{}\mathrm{Zr}$, ${}_{}{}^{119}{}_{}{}^{}\mathrm{Sn}$, ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$, and ${}_{}{}^{209}{}_{}{}^{}\mathrm{Bi}$ are compared with the predictions of exact solutions of the coupled Lane equations, and it is found that the distorted-wave Born-approximation and coupled-channel predictions have essentially the same overall shape if the same optical and symmetry potentials are used. A linear energy dependence of the complex symmetry potential, suggested earlier from distorted-wave Born-approximation analyses, as well as modification of the neutron optical potential are required to describe the available data from threshold to ∼45 MeV if global optical parameters are used.