N15(p,γ2γ)O16and the Deformed Giant Resonance inO16

Abstract

The cascade $\ensuremath{\gamma}$-ray decay of states at 19.9 and 20.4 MeV in $^{16}\mathrm{O}$ has been observed using the reaction $^{15}\mathrm{N}(p,{\ensuremath{\gamma}}_{2}\ensuremath{\gamma})^{16}\mathrm{O}$. These states appear to have the properties expected of giant dipole states based on the ${J}^{\ensuremath{\pi}}={3}^{\ensuremath{-}}$ state at 6.13 MeV. Together with earlier work, the result implies that giant dipole states based on the ${J}^{\ensuremath{\pi}}={0}^{+}$ state at 6.05 MeV are displaced significantly from the energies expected from a simple weak-coupling model.