Gamma and alpha emission from the 15-Mev level of ${\mathrm{C}}^{12}$ is investigated in the reaction ${\mathrm{B}}^{11}(d, n){\mathrm{C}}^{12*}$. An upper limit on the ratio of $\alpha$- to $\gamma$-radiation from the state is $\frac{{\Gamma }_{\alpha }}{{\Gamma }_{\gamma }}<1.5\mathrm{}$. The excitation threshold for 15-Mev gamma radiation is 1.633±0.003 Mev, and the cross section is given as a function of bombarding energy up to 3.25 Mev. Resonances are found at 2.180±0.010 and 3.080±0.015 Mev. Momentum analyses of $\alpha$ particles from deuteron bombardment of ${\mathrm{B}}^{10}$ and natural boron reveal no excited states in ${\mathrm{Be}}^8$ in the range of excitation 9.8 to 14.8 Mev, and no new states in ${\mathrm{Be}}^9$ below 4.7-Mev excitation. The nature of the 1.75-Mev level of ${\mathrm{Be}}^9$ is discussed. The branching of the $\beta$-decay of ${\mathrm{B}}^{12}$ to the 4.43-Mev state of ${\mathrm{C}}^{12}$ is found to be 1.4±0.4%, allowing the unique assignment $J=1^{+}$ to the ${\mathrm{B}}^{12}$ ground state, which is presumed to be the analog of the 15-Mev state of ${\mathrm{C}}^{12}$. Upper limits of (0.00±0.01) and (0.1±0.1)%, respectively, are found for $\gamma$ rays with $E_{\gamma }>6\mathrm{}$ Mev and $E_{\gamma }=3.2\mathrm{}$ Mev following ${\mathrm{B}}^{12}$ decay. The cross section for the production of ${\mathrm{B}}^{12}$ is given as a function of bombarding energy for $0.5<~E_d<~3.25$ Mev.

• Received 16 June 1958

DOI:https://doi.org/10.1103/PhysRev.112.503