Parity non-conservation in the alpha particle decay of the 8.87 MeV2−state ofO16

The energy spectrum of 2.5×${10}^8$ $\alpha$ particles from the sequential decay ${}_{}{}^{16}{}_{}{}^{}\mathrm{N}\left({\beta }^{-}\right){}_{}{}^{16}{}_{}{}^{}\mathrm{O}\left(\alpha \right){}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ has been analyzed. Superimposed on the broad energy distribution which originated from the decay of the $1^{-}$ 9.60 MeV state of ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ into ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}+\alpha$, a group of 9538 ± 1810 $\alpha$ particles with an energy of 1282 keV has been identified with a maximum error of ± 5 keV. This group is attributed to the parity non-conserving decay from the $2^{-}$ 8.87 MeV state of ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ into ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}+\alpha$; the $\alpha$-particle emission width for this decay has been determined to be ${\Gamma }_{\alpha }$ = (1.03 ± 0.28) × ${10}^{-10\mathrm{}}$ eV. In a separate measurement the relative ${}_{}{}^{16}{}_{}{}^{}\mathrm{N}$ $\beta$ decay branching ratio to the 9.60 and 8.87 MeV states in ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$, which was necessary for the calculation of ${\Gamma }_{\alpha }$, has been determined to be (9.98 ± 0.70) × ${10}^{-4\mathrm{}}$.