Proton capture byN15above the giant dipole resonance

The proton capture cross sections to the ground and excited states of ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ have been measured at several angles in the proton energy interval between 18 and 40 MeV. The ground state angular distribution, which shows a significant $E1-E2\mathrm{}$ interference effect above 40 MeV, results in reasonable agreement with semidirect capture calculations. Transitions to final bound and unbound 1p-1h states in ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ having a dominant $1p_{\frac{1}{2}}^{-1\mathrm{}}$ hole have also been measured. Resonances built on these residual states have been systematically observed above $E_{\mathrm{p}}=20\mathrm{}$ MeV; the possible interpretation of these states as giant dipole resonances built on excited states is discussed.