The 60° and 90° yield curves for the ${}_{}{}^{11}{}_{}{}^{}\mathrm{B}$($p$,$\gamma$)${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ reaction have been measured for $E_p=2.9\mathrm{} \mathrm{to} 4.6$ MeV in 100 keV steps for $\gamma$ rays leading to the ground and first and third excited states. Recent ($\pi$,${\pi }^{\prime }$) data suggest the existence of an isospin mixed doublet near 19.5 MeV in ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$. A continuum shell model calculation which successfully describes the ($\pi$,${\pi }^{\prime }$) data predicts an observable effect in the ${\gamma }_3$ channel. However, no evidence for these states is found in our ${\gamma }_3$ data.

NUCLEAR REACTIONS ${}_{}{}^{11}{}_{}{}^{}\mathrm{B}$($p$,$\gamma$)${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$; measured $\sigma \left(E_p\right)$, $E_p=2.9\mathrm{} \mathrm{to} 4.6$ MeV, $\theta =60\mathrm{}°, 90°$, for ${\gamma }_0$, ${\gamma }_1$, ${\gamma }_3$. Compared ${\gamma }_3$ data to continuum shell model calculations. No evidence for 19.25 and/or 19.65 MeV states is found.

• Received 18 January 1982

DOI:https://doi.org/10.1103/PhysRevC.25.2823