The mechanism of the reactions ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}({}_{}{}^3{}_{}{}^{}\mathrm{He}, \alpha ){}_{}{}^{11}{}_{}{}^{}\mathrm{C}$ leading to the ${\frac{3}{2}}^{-}$ ground state and ${\frac{5}{2}}^{-}$ second excited state of ${}_{}{}^{11}{}_{}{}^{}\mathrm{C}$ is studied using finite-range distorted-wave Born approximation with all one-step direct and exchange processes. By taking into account in detail the cluster structure of ${}_{}{}^{11}{}_{}{}^{}\mathrm{C}$ and ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, the transition to the ${\frac{5}{2}}^{-}$ state which is a $j$ forbidden direct process can be explained well by the exchange process.

NUCLEAR REACTIONS ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}({}_{}{}^3{}_{}{}^{}\mathrm{He}, \alpha ){}_{}{}^{11}{}_{}{}^{}\mathrm{C}$, finite-range distorted-wave Born approximation analysis, direct and exchange processes, cluster structure.

• Received 3 August 1982

DOI:https://doi.org/10.1103/PhysRevC.26.2323