An intermediate-image pair spectrometer was used to study electromagnetic transitions in ${\mathrm{Be}}^{10}$ and ${\mathrm{B}}^{10}$. Energy levels in these nuclei were populated by means of the ${\mathrm{Be}}^9(d, p){\mathrm{Be}}^{10}$ and ${\mathrm{Be}}^9(d, n){\mathrm{B}}^{10}$ reactions with deuteron energies between 2.0 and 3.2 MeV. In ${\mathrm{Be}}^{10}$ the branching ratios of the 5.96→0 and 5.96→3.37 transitions were determined to be 48±2% and 52±2%, respectively. A pair line corresponding to the 6.26→3.37 transition was observed and an upper limit of 0.4% was placed on the relative intensity of the 6.26→0 transition which supports an assignment of $2^{-}$ for the ${\mathrm{Be}}^{10}$ 6.26-MeV level. In addition, a 6.18→0 transition was observed but not a 6.18→3.37 transition. The energy difference between the 6.18→0 pair line and the 5.96→0 pair line was measured with sufficient accuracy to show that the ${\mathrm{Be}}^{10}$ 6.18-MeV level has a mean lifetime greater than 5×${10}^{-13\mathrm{}}$sex, and consequently has a most probable spin-parity assignment of ${\mathrm{O}}^{+}$. In ${\mathrm{B}}^{10}$ the relative intensities of the 3.58→0.72 and 3.58→0 transitions were found to be (4.2±0.3): 1 if both transitions are $M1\mathrm{}$ while the branching ratios of the 5.16→2.15, 5.16→0.72, and 5.16→0 transitions were found to be (65±2)%, (29.5±2)%, and (5.5±0.7)%, respectively. Transitions from the ${\mathrm{B}}^{10}$ 4.77-MeV level were not observed and a limit of $\frac{{\Gamma }_{\gamma }}{\Gamma }<0.05\mathrm{}$ was set for this $\alpha$-particle unbound level. Data are presented to enable $\frac{{\Gamma }_{\gamma }}{\Gamma }$ for the 5.16-MeV level of ${\mathrm{B}}^{10}$ to be computed when the relative production cross sections of that state and the 3.37-MeV state of ${\mathrm{Be}}^{10}$ in deuteron bombardments become known. In order to obtain these results, calculations of the spectrometer pair-line efficiency were extended to include the emission of internal pairs from aligned nuclei. The experimental results are compared to the predictions of the independent-particle model.

• Received 3 June 1963

DOI:https://doi.org/10.1103/PhysRev.132.776