Excitation functions at nine angles for the reaction ${\mathrm{N}}^{15}(p, {\alpha }_0){\mathrm{C}}^{12}$ are reported for incident proton energies from 0.9 to 1.3 Mev. At a laboratory angle of 140° the excitation function has been extended to 2.9 Mev. In addition to previously reported resonances near 1.03 and 1.21 Mev, corresponding to ${\mathrm{O}}^{16}$ states at 13.08 and 13.24 Mev, an anomalous behavior is observed near 1.87 Mev. Additional evidence for such behavior near this energy has been obtained from the ${\mathrm{N}}^{15}(p, {\alpha }_1\gamma ){\mathrm{C}}^{12}$ reaction. The qualitative features of the ${\mathrm{N}}^{15}(p, {\alpha }_0){\mathrm{C}}^{12}$ data are shown to be consistent with the assignments $J=1^{-}$, $J=1^{-}$, and $J=3^{-}$ for the 0.34, 1.03, and 1.21-Mev resonances respectively. Fitting Breit-Wigner curves to the measured excitation function of ${\mathrm{N}}^{15}(p, {\alpha }_1\gamma ){\mathrm{C}}^{12}$ near 1.64 and 1.98 Mev has yielded $E_R=1.640\mathrm{}\pm 0.003$ Mev ($\Gamma =68\mathrm{}\pm 3$ kev) and $E_R=1.979\mathrm{}\pm 0.003$ Mev ($\Gamma =23\mathrm{}\pm 2$ kev) for these previously reported resonances (${\mathrm{O}}^{16}$ states at 13.65 and 13.97 Mev). It is shown that $\frac{{\Gamma }_p}{\Gamma }\ll 1$ for the resonance at 1.98 Mev.

• Received 7 August 1957

DOI:https://doi.org/10.1103/PhysRev.108.1015