Electromagnetic transitions in ${\mathrm{N}}^{15}$ and ${\mathrm{O}}^{15}$ have been investigated following the population of the bound levels of these nuclei by ${\mathrm{N}}^{14}$+$d$, ${\mathrm{C}}^{14}$+$d$, ${\mathrm{C}}^{13}$+${\mathrm{He}}^3$, and ${\mathrm{O}}^{16}$+${\mathrm{He}}^3$ with bombarding energies from 1.9 to 6.7 MeV. Gamma-ray angular distributions and relative intensities were determined using a three-crystal pair spectrometer. Gamma-ray branching ratios in ${\mathrm{N}}^{15}$ were determined through measurements of proton-gamma coincidence spectra following the ${\mathrm{N}}^{14}(d, p){\mathrm{N}}^{15*}$ and ${\mathrm{C}}^{13}({\mathrm{He}}^3, p){\mathrm{N}}^{15*}$ reactions. The ratios of radiative width to total width for the unbound 10.45- and 10.81-MeV levels of ${\mathrm{N}}^{15}$ were obtained as $\frac{{\Gamma }_{\gamma }}{\Gamma }>0.7\mathrm{}$ and $\frac{{\Gamma }_{\gamma }}{\Gamma }={{0.55}_{-0.15\mathrm{}}}^{+0.25\mathrm{}}$, respectively. Gamma-ray branching ratios in ${\mathrm{N}}^{15}$ and ${\mathrm{O}}^{15}$ were determined from measurements of gamma-gamma coincidence spectra using ${\mathrm{N}}^{14}$+$d$, ${\mathrm{C}}^{14}$+$d$, and ${\mathrm{O}}^{16}$+${\mathrm{He}}^3$. Evidence was found for an excitation energy for the sixth excited state of ${\mathrm{O}}^{15}$ of 7.284±0.007 MeV, rather than 7.17±0.05 MeV as previously reported. Singles gamma-ray spectra were measured from all four targets using a lithium-drifted germanium detector. In these measurements, gamma-ray cascades to the 5.3-MeV doublet of ${\mathrm{N}}^{15}$ were separated, and it was determined that all the bound levels of ${\mathrm{N}}^{15}$ and ${\mathrm{O}}^{15}$ except the ${\mathrm{N}}^{15}$ 5.270- and ${\mathrm{O}}^{15}$ 5.240-MeV levels have mean lifetimes less than 5×${10}^{-13\mathrm{}}$ sec. An intermediate-image magnetic spectrometer was used to study the angular correlation of internal pairs for ten ground-state transitions in ${\mathrm{N}}^{15}$ and ${\mathrm{O}}^{15}$. From this work it was determined that the ${\mathrm{N}}^{15}$ 8.57-MeV level has $J^{\pi }={\frac{3}{2}}^{+}$, the ${\mathrm{N}}^{15}$ 9.06- and 10.07-MeV levels have $J^{\pi }={\frac{1}{2}}^{+} or {\frac{3}{2}}^{+}$, or the 9.76- and 9.93-MeV levels are most probably $J^{\pi }={\frac{1}{2}}^{+} or {\frac{3}{2}}^{+}$, and the 9.16-MeV level is most probably $J^{\pi }={\frac{3}{2}}^{-}$. For the remaining levels the measurements serve to restrict the range of possible spin-parity assignments. The correspondence between mirror levels in ${\mathrm{N}}^{15}$ and ${\mathrm{O}}^{15}$ is discussed and a comparison with theoretical predictions is made.

• Received 23 July 1965

DOI:https://doi.org/10.1103/PhysRev.140.B1202