Proton radiative capture reactions on ${}_{}{}^{11}{}_{}{}^{}\mathrm{B}$ targets are calculated assuming a direct capture mechanism. This is used to predict ($p$,$\gamma$) transitions leading to the ground state of ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, and to high-lying excited states at about 19 MeV excitation in ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$. The results are compared with recent experimental data. The theoretical cross sections are the same magnitude as the data, but do not properly reproduce the energy dependence of the capture cross sections. There appears to be an important "semidirect" component to the ($p$,$\gamma$) reaction leading to high-lying states in ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$. We have also applied the same theory to calculate ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$($\gamma$,$p_0$)${}_{}{}^{11}{}_{}{}^{}\mathrm{B}$ and ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$($\gamma$,$n_0$)${}_{}{}^{11}{}_{}{}^{}\mathrm{C}$ transitions which have been previously measured.

NUCLEAR REACTIONS ($p$,$\gamma$) and ($\gamma$,$p$) reactions at medium energies; direct capture; states of high excitation energy in ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$; photodisintegration of ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$.

• Received 13 May 1981

DOI:https://doi.org/10.1103/PhysRevC.25.1722