Levels of ${}_{}{}^{12}{}_{}{}^{}\mathrm{Be}$ have been studied using the ${}_{}{}^{10}{}_{}{}^{}\mathrm{Be}\mathrm{}(t,p)\mathrm{}{}_{}{}^{12}{}_{}{}^{}\mathrm{Be}$ reaction. The spin of an excited state at $E_x=2.110\mathrm{}\pm 0.015$ MeV is determined model independently as $J=2\mathrm{}$ using a measurement of the proton-$\gamma$ angular correlation in an axially symmetric geometry. A mechanically chopped beam was used to study $\beta$ activity following the irradiation of ${}_{}{}^{10}{}_{}{}^{}\mathrm{Be}$ by 12 MeV tritons. A least squares analysis of the resulting decay curve yields $T_{\frac{1}{2}}\left({}_{}{}^{12}{}_{}{}^{}\mathrm{Be}\right)=24.4\mathrm{}\pm 3.0$ msec. A ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ neutron detector was used to search for delayed neutrons; a 1σ upper limit on a delayed neutron branch of 1% is obtained. The above results support the suggestion that low-lying states in ${}_{}{}^{12}{}_{}{}^{}\mathrm{Be}$ involve the excitation of particles into the $1s-0d$ shell.

NUCLEAR REACTIONS ${}_{}{}^{10}{}_{}{}^{}\mathrm{Be}(t,p\gamma )$, $E=12\mathrm{}$ MeV measured $\sigma \left(E_p\right)$, $p\gamma \left(\theta \right)$, $E_{\gamma }$. ${}_{}{}^{12}{}_{}{}^{}\mathrm{Be}$ deduced levels, $J$, $\pi$. Enriched target.

RADIOACTIVITY ${}_{}{}^{12}{}_{}{}^{}\mathrm{Be}$ [from ${}_{}{}^{10}{}_{}{}^{}\mathrm{Be}\mathrm{}(t,p)\mathrm{}$]; measured $T_{\frac{1}{2}}$ from $\beta$ activity. Searched for delayed neutrons.

• Received 9 December 1977

DOI:https://doi.org/10.1103/PhysRevC.17.1525