Observation of a nuclear rainbowlike phenomenon in the (He3,t) charge-exchange reaction

Using a beam of 72 MeV helions, wide-range angular distributions were recorded for the charge-exchange reaction ${}_{}{}^{14}{}_{}{}^{}\mathrm{C}({}_{}{}^3{}_{}{}^{}\mathrm{He},t){}_{}{}^{14}{}_{}{}^{}\mathrm{N}$ to the ground, analog, and Gamow-Teller states of ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$. At far-side-dominated larger scattering angles, pronounced rainbowlike bumps are observed for the first time in charge-exchange channels, but shifted somewhat forwards compared with the elastic scattering. A distorted-wave Born approximation analysis shows substantial sensitivity to the charge-exchange form factors as well as to the choice of triton versus helion optical potentials.