Particle configurations of giant $E1$ states in the ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}(\gamma ,p_2)$ and ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}(\gamma ,p_0)$ processes

Angular distributions and absolute cross sections have been measured for the ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}(\gamma ,p_2)$ and ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}(\gamma ,p_0)$ reactions, at giant resonance energies. The angular distributions are shown to be consistent with a model in which exclusively ${\left(p_{\frac{1}{2}}\right)}^{-1\mathrm{}}\left(2s1d\right)$ giant dipole states populate the ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ ground state by proton decay, and predominantly ${\left(p_{\frac{3}{2}}\right)}^{-1\mathrm{}}\left(2s1d\right)$ giant dipole states feed the ${\frac{3}{2}}^{-}$ state of ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ at 3.68 MeV. Branching calculations based on established spectroscopic factors further support this model. It is inferred that the ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$ dipole states of ${\left(p_{\frac{3}{2}}\right)}^{-1\mathrm{}}\left(2s1d\right)$ character, which carry ∼90% of the $E1$ strength and which dominate the ($\gamma ,p_2$) process studied, do not contribute significantly to the ($\gamma ,p_0$) process which has often previously been treated as representative of $E1$ absorption.

NUCLEAR REACTIONS ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}(\gamma ,p_2)$, ($\gamma ,p_0$), $E_{\gamma }=19\mathrm{}-25$ MeV; measured $\sigma (E_{\gamma };E_p;\theta )$. Deduced $E2$, $M1$ excitation strength. Inferred parent $E1$ configurations.