The 3.39-MeV state in ${\mathrm{B}}^{12}$ has been studied in the ${\mathrm{B}}^{11}+n$ system, where the state appears as a resonance at a (lab) neutron energy of 20.8±0.5 keV. Comparison of the neutron scattering and transmission measurements with the ${\mathrm{B}}^{11}\mathrm{}(d,p)\mathrm{}$ data requires that the resonance be $d$ wave. Various considerations leave $3^{-}$ as the only plausible assignment. For a spin of 3, the neutron width is ${\Gamma }_n=3.1\mathrm{}\pm 0.6$ eV, which is about equal to the Wigner limit. Neutron-capture measurements, in which the residual ${\mathrm{B}}^{12}$ activity was observed, clearly showed the resonance and yielded a total radiation width ${\Gamma }_{\gamma }=0.025\mathrm{}\pm 0.008$ eV. The 18.36-MeV state in ${\mathrm{C}}^{12}$ appears to be the $T_z=0\mathrm{}$ analog of this state.

• Received 9 October 1968

DOI:https://doi.org/10.1103/PhysRev.178.1612