Taking into account the final-state density of the leptons, a single resonance model for the ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}+\alpha 1^{-}$ scattering amplitude predicts a markedly asymmetric peak in the $\alpha$ spectrum following ${}_{}{}^{16}{}_{}{}^{}\mathrm{N}\beta$ decay into continuum states of ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$. The observed peak is nearly symmetric and it is shown that this symmetry can arise from destructive interference from the subthreshold $1^{-}$ state (7.12 MeV) and/or a background from states of ∼17-MeV excitation in ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$. It is shown that the $\alpha$ width of the 7.12-MeV state must be an order of magnitude smaller than that of the $1^{-}$ state (9.58 MeV).

• Received 1 May 1971

DOI:https://doi.org/10.1103/PhysRevC.4.1591