Bound states of ${\mathrm{Be}}^{10}$, ${\mathrm{B}}^{11}$, ${\mathrm{B}}^{12}$, and ${\mathrm{B}}^{13}$ were formed by bombardment of ${\mathrm{Li}}^7$ with 3-MeV ${\mathrm{Li}}^7$ ions and were studied by two-parameter analysis. Gamma radiation from these states and particles associated with their production were measured in coincidence. A 256×256-channel two-parameter analyzer made up of a general purpose computer and two 256-channel pulse-height analyzers was used. The gamma-ray emission from individual bound states of the above nuclei was obtained uncontaminated by cascade feeding of levels. Gamma-ray branching ratios of levels in ${\mathrm{Be}}^{10}$ and ${\mathrm{B}}^{11}$ confirm previous measurements. Gamma-ray branching ratios of the bound levels of ${\mathrm{B}}^{12}$ and ${\mathrm{B}}^{13}$ were measured for the first time. The pattern of gamma-ray branching ratios of ${\mathrm{B}}^{13}$ bears a certain resemblance to that for ${\mathrm{B}}^{11}$. The first excited state of ${\mathrm{B}}^{13}$ previously believed to be at 3.70 MeV was found to be a doublet at 3.50±0.05 MeV and 3.70±0.05 MeV.

• Received 29 March 1963

DOI:https://doi.org/10.1103/PhysRev.131.1204