Nuclear Surface Effects in the Giant Dipole Resonances of Closed-Shell Nuclei

The theory of collective correlations for giant resonances interacting with surface vibrations is extended to nuclei with closed-shell (nonvibrating) ground-state configurations. Electromagnetic transition matrix elements are calculated for dipole transitions in ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ and ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$. For both nuclei the results are in good agreement with experimental photonuclear cross-section measurements.