Cross sections for the production of the light elements lithium, beryllium, and boron by proton bombardment of ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ were measured for proton energies between 21.7 and 44.0 MeV. Time-of-flight methods were used to identify the masses of ions recoiling from a thin target into a semiconductor detector. The results are related to current models on the origin of these light elements, and are consistent with a suggestion that the ${}_{}{}^{11}{}_{}{}^{}\mathrm{B}$/${}_{}{}^{10}{}_{}{}^{}\mathrm{B}$ isotopic ratio has remained unaltered at its formation value.

• Received 30 July 1969

DOI:https://doi.org/10.1103/PhysRevC.1.270