The energy spectrum of 1.3 × ${10}^8$ $\alpha$ particles from the sequential decay ${}_{}{}^{16}{}_{}{}^{}\mathrm{N}\left({\beta }^{-}\right){}_{}{}^{16}{}_{}{}^{}\mathrm{O}\left(\alpha \right){}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ has been obtained. A group of 7100±1800 $\alpha$ particles with an energy of 1278±10 keV has been identified. They are attributed to the parity-forbidden decay from the ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ 8.87-MeV $2^{-}$ state into ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}+\alpha$. A width ${\Gamma }_{\alpha }=(1.8\mathrm{}\pm 0.8)\times {10}^{-10\mathrm{}}$ eV has been obtained for this transition.

• Received 3 August 1970

DOI:https://doi.org/10.1103/PhysRevLett.25.941