Study of Giant Resonances Through Radiative Pion Capture with Application toO16

Using a generalized Goldhaber-Teller model of the giant multipole resonance in ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$, we have evaluated radiative pion-capture rates from $1s$ and $2p$ orbits, leading to various multipole isospin states in ${}_{}{}^{16}{}_{}{}^{}N$, and obtained the corresponding $\gamma$ spectra. The subsequent neutron emission was considered on the basis of Wigner's $R$-matrix theory. Whereas in $1s$ capture, the spectra are dominated by the dipole resonances, in the $2p$ capture there is an even stronger contribution from the $2^{+}$ and $3^{+}$ quadrupole states. The total radiative capture rate compares favorably with experiment.