Decay Modes ofO16Giant Resonance States

A Ge(Li) detector has been used to observe de-excitation $\gamma$ rays from ${\mathrm{O}}^{15}$ and ${\mathrm{N}}^{15}$ following the photodisintegration of ${\mathrm{O}}^{16}$ at giant resonance energies. Significant branching to the (${\mathrm{½}}^{+}$, ${\frac{5}{2}}^{+}$) states near 5 MeV implies a departure from a single-particle, single-hole $E1\mathrm{}$ absorption process.