Weakly excited resonance levels in the 13C(p, γ) 14N reaction

Abstract

Three midget resonances in the 13C(p, γ) 14N reaction were observed at E p = 1012±2 keV, 1523±2 keV and 1701±1 keV corresponding to 14N excitation energies of 8.489, 8.963 and 9.129 MeV, respectively. The 8.489 MeV state decays by γ-ray emission predominantly to the 5.10 MeV state with an angular distribution, W( θ) = 1 + (0.59 ± 0.06) P 2 (cos θ) − (0.46 ± 0.10) P 4 (cos θ). This angular distribution together with the observed γ-ray width ( ωΓ γ ≊ 0.01 eV ) and branching ratios determine that J π = 4 −, T = 0 for this level. The 8.963 MeV level decays by γ-ray emission at least two-thirds to the 6.44 MeV state. This fact and the small transition rate ( ωΓ γ ≊ 0.003 eV ) identify the level as 5 +. The only observed transition ( ≧80%) from the 9.129 MeV level is to the ground state ( ωΓ γ ≊ 0.03 eV ) with an angular distribution, W( θ) = 1 + (0.22 ± 0.09) P 2 (cos θ). These data establish J π = 2 −, T = 0 for this level. Arguments are given for shell-model assignments to these levels.