Spins, parities, and ${\alpha }_0$-decay branching ratios have been determined for a number of states in ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ and ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$ using the ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$(${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^8{}_{}{}^{}\mathrm{Be}$)${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$*(${\alpha }_0$)${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ and ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$(${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^8{}_{}{}^{}\mathrm{Be}$)${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$*(${\alpha }_0$)${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ reactions. The ${}_{}{}^8{}_{}{}^{}\mathrm{Be}$ nuclei were detected at 0°, and the alpha particles from the decay of the excited states formed in the (${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^8{}_{}{}^{}\mathrm{Be}$) reactions were detected over the range $40°\le {\theta }_{\mathrm{lab}}\le 97°$, typically corresponding to a range in the heavy-recoil center-of-mass system of $50°\le {\theta }_{\mathrm{RCM}}\le 120°$. Structure observed at an excitation energy of 22.5±0.5 MeV in ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ appears to correspond to an $8^{+}$ state which is then a candidate for identification as the $8^{+}$ member of the $K^{\pi }=0^{+}, 4\mathrm{p}-4\mathrm{}\mathrm{h}$ rotational band. In ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$ we have confirmed a number of spin assignments for states below 16 MeV in excitation, and in addition we have made the following assignments: 16.63 MeV ($7^{-}$), 17.3 MeV ($8^{+}$), 21.08 MeV ($9^{-}$), and 22.87 MeV ($9^{-}$). All of the ${\alpha }_0$ branching ratios for the strongly populated states in ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$ are found to be roughly 100%, with the exception of those for the 17.3 MeV ($8^{+}$) and 21.08 MeV ($9^{-}$) levels which are found to be 40% and 65%, respectively.

NUCLEAR REACTIONS ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$(${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^8{}_{}{}^{}\mathrm{Be}$)${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$*(${\alpha }_0$)${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$(${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^8{}_{}{}^{}\mathrm{Be}$) ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$*(${\alpha }_0$)${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$, particle-particle angular correlations; $E_{\mathrm{lab}}=78\mathrm{}$ MeV, ${\theta }_{{}_{}{}^8{}_{}{}^{}\mathrm{Be}}\approx 0°$. Deduce $J^{\pi }$, $\frac{{\Gamma }_{{\alpha }_0}}{{\Gamma }_{\mathrm{total}}}$.

• Received 14 May 1979

DOI:https://doi.org/10.1103/PhysRevC.20.1743