Cross sections have been measured for the production of ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$, ${}_{}{}^9{}_{}{}^{}\mathrm{Be}$, and ${}_{}{}^{10}{}_{}{}^{}\mathrm{B}$ in proton reactions on ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$, at energies extending from threshold to 18 MeV. The reaction products were identified by time-of-flight techniques, and total cross sections were determined by integrating over the measured angular distributions. Although the typical abundance of ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ in nature is small compared to that of ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$, or ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$, the ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ reactions may have a significant role in the production of the light elements because of their low $Q$ values. Even for a ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$/${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ ratio as low as the terrestrial ratio of 0.01, the inclusion of ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ contributions is found to reduce appreciably the $\frac{7}{6}$, $\frac{11}{10}$, and Li/Be abundance ratios calculated for interactions at low energies between protons and a representative mixture of C, N, and O. Over-all, this reduction brings the abundance ratios calculated at proton energies below 25 MeV closer to the observed solar system ratios.

NUCLEAR REACTIONS ${}_{}{}^{15}{}_{}{}^{}\mathrm{C}(p, \alpha )$, $E=5-18\mathrm{}$ MeV; ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}(p, 2\alpha )$, $E=10-18\mathrm{}$ MeV; ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}(p, p\alpha )$, $E=13-18\mathrm{}$ MeV; measured $\sigma \left(\theta \right)$, $\sigma \mathrm{}\left(E\right)\mathrm{}$, $\sigma$. Astrophysical production of LiBeB.

• Received 18 July 1974

DOI:https://doi.org/10.1103/PhysRevC.11.410