Cross sections fo the production of $A=6, 7, 9, 10, \mathrm{and} 11$ isobars in the reaction of 50-90 MeV protons with oxygen are reported. Product masses were identified by time-of-flight techniques using either a channel-plate fast-timing device or rf fast timing. Mass, kinetic energy, and angular distributions are reported for the products. The measured cross sections are applied to theories of LiBeB nucleosynthesis which involve galactic-cosmic-ray or stellar-flare reactions as a source of these elements. Both of the models underproduce the observed ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$/${}_{}{}^6{}_{}{}^{}\mathrm{Li}$ ratio by an order of magnitude, which supports previous conclusions that an additional source of ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$ is required for its synthesis. However, the models give reasonable agreement for the ${}_{}{}^{11}{}_{}{}^{}\mathrm{B}$/${}_{}{}^{10}{}_{}{}^{}\mathrm{B}$, ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$/Be and B/${}_{}{}^6{}_{}{}^{}\mathrm{Li}$ ratios, although the galactic ray model predicts a ${}_{}{}^{11}{}_{}{}^{}\mathrm{B}$/${}_{}{}^{10}{}_{}{}^{}\mathrm{B}$ ratio that is low by a factor of 2. In addition the B/${}_{}{}^6{}_{}{}^{}\mathrm{Li}$ ratio is consistent only with a low value for the natural boron abundance.

NUCLEAR REACTIONS ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$($p$,HI); HI Mass numbers $A=6, 7, 9, 10, \mathrm{and} 11$; $E=50, 55, 65, 75, 90$ MeV; ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$, ${}_{}{}^7{}_{}{}^{}\mathrm{Be}$, ${}_{}{}^{10}{}_{}{}^{}\mathrm{Be}$, ${}_{}{}^{10}{}_{}{}^{}\mathrm{B}$, and ${}_{}{}^{10}{}_{}{}^{}\mathrm{C}$ at 90 MeV; measured $\sigma$, $\sigma \left(\theta \right)$, and $\sigma \mathrm{}\left(E\right)\mathrm{}$; astrophysical implications of data are discussed.

• Received 17 July 1978

DOI:https://doi.org/10.1103/PhysRevC.19.631