Optical-model potential in single-nucleon-transfer reactions induced by heavy ions

Abstract

Elastic scattering angular distributions were measured for ${}_{}{}^{48}{}_{}{}^{}\mathrm{Ca}$ + ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ at 56 MeV and for ${}_{}{}^{45}{}_{}{}^{}\mathrm{Sc}$ + ${}_{}{}^{15}{}_{}{}^{}\mathrm{N}$ at 47.53 MeV. Extensive searches and systematic analyses of the optical-model potentials were performed to study ambiguities. Various potential sets that fit elastic scattering were used in distorted-wave Born approximation calculations of single-nucleon transfers. To a high degree the optical potential ambiguities that exist for elastic scattering persist for the transfer predictions. The distorted-wave Born approximation calculations are compared to experimental angular distributions of the single-proton-transfer reactions ${}_{}{}^{48}{}_{}{}^{}\mathrm{Ca}$(${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$, ${}_{}{}^{15}{}_{}{}^{}\mathrm{N}$)${}_{}{}^{49}{}_{}{}^{}\mathrm{Sc}$ and ${}_{}{}^{48}{}_{}{}^{}\mathrm{Ca}$(${}_{}{}^{19}{}_{}{}^{}\mathrm{F}$, ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}$)${}_{}{}^{49}{}_{}{}^{}\mathrm{Sc}$ at 56 MeV and ${}_{}{}^{48}{}_{}{}^{}\mathrm{Ca}$(${}_{}{}^{15}{}_{}{}^{}\mathrm{N}$, ${}_{}{}^{14}{}_{}{}^{}\mathrm{C}$)${}_{}{}^{49}{}_{}{}^{}\mathrm{Sc}$ at 48 MeV. The transfers are well predicted by the distorted-wave Born approximation when there is $l$ matching between the entrance and exit channel dominant partial waves. For cases of $l$ mismatch the calculations do not reproduce the data. This disagreement cannot be removed by changes in the optical potentials, if these are still required to described elastic scattering. These results suggest the possible presence of reaction processes other than those treated in the conventional distorted-wave Born approximation amplitude.