States inO16between 12.67 and 13.80 Mev

Abstract

A study of the elastic scattering of protons from ${\mathrm{N}}^{15}$ is reported for proton energies between 600 and 1800 kev and for scattering angles from 75° to 160°. The technique for the preparation of the ${\mathrm{N}}^{15}$ targets is discussed. Anomalies in the scattering cross section are observed near incident proton energies of 710, 898, 1028, 1210, and 1640 kev, corresponding to states in ${\mathrm{O}}^{16}$ from 12.78 to 13.65 Mev. Analysis of these scattering data leads to the assignments $J=0^{-}$, $J=2^{-}$, $J=1^{-}$, $J=3^{-}$, and $J=1^{+}$ for the 710, 898, 1028, 1210, and 1640-kev states respectively. These assignments agree with earlier work except for the 710-kev resonance, which is reported here for the first time, and the 1210-kev level, which was previously reported to be $J=4^{+}$. The angular distribution of the $\alpha$-particles resonant at 1210 kev from the reaction ${\mathrm{N}}^{15}(p, {\alpha }_1\gamma )C^{12}$ has been remeasured and requires $J=4^{+}$ as was found previously. However, a measurement of the $\alpha -\gamma$ angular correlation function at 1210 kev is found to be consistent with $J=3^{-}$ but not $J=4^{+}$. This discrepancy has not been resolved, but the evidence favoring the assignment $J=3^{-}$ is quite strong. Suggestions for the isotopic spin quantum numbers for these five states in ${\mathrm{O}}^{16}$ are made.