Further Investigation ofN15+pReactions

Abstract

Excitation functions at nine angles for the reaction ${\mathrm{N}}^{15}(p, {\ensuremath{\alpha}}_{0}){\mathrm{C}}^{12}$ are reported for incident proton energies from 0.9 to 1.3 Mev. At a laboratory angle of 140\ifmmode^\circ\else\textdegree\fi{} 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 ${\mathrm{N}}^{15}(p, {\ensuremath{\alpha}}_{1}\ensuremath{\gamma}){\mathrm{C}}^{12}$ reaction. The qualitative features of the ${\mathrm{N}}^{15}(p, {\ensuremath{\alpha}}_{0}){\mathrm{C}}^{12}$ data are shown to be consistent with the assignments $J={1}^{\ensuremath{-}}$, $J={1}^{\ensuremath{-}}$, and $J={3}^{\ensuremath{-}}$ for the 0.34, 1.03, and 1.21-Mev resonances respectively. Fitting Breit-Wigner curves to the measured excitation function of ${\mathrm{N}}^{15}(p, {\ensuremath{\alpha}}_{1}\ensuremath{\gamma}){\mathrm{C}}^{12}$ near 1.64 and 1.98 Mev has yielded ${E}_{R}=1.640\ifmmode\pm\else\textpm\fi{}0.003$ Mev ($\ensuremath{\Gamma}=68\ifmmode\pm\else\textpm\fi{}3$ kev) and ${E}_{R}=1.979\ifmmode\pm\else\textpm\fi{}0.003$ Mev ($\ensuremath{\Gamma}=23\ifmmode\pm\else\textpm\fi{}2$ kev) for these previously reported resonances (${\mathrm{O}}^{16}$ states at 13.65 and 13.97 Mev). It is shown that $\frac{{\ensuremath{\Gamma}}_{p}}{\ensuremath{\Gamma}}\ensuremath{\ll}1$ for the resonance at 1.98 Mev.