Radiative strength function and the pygmy dipole resonance in $^{208}$Pb and $^{70}$Ni

The pygmy-resonance parameters and the $E1$ strength function are derived for $^{208}\mathrm{Pb}$ using a fully self-consistent microscopic formalism recently developed for magic nuclei, which takes into account quasiparticle phonon interactions (or coupling to phonons) in addition to the random phase approximation. For the radiative strength function of $^{208}\mathrm{Pb}$ at energies above $5$ MeV, the experimental data of the Oslo group are adequately described by our predictions, whereby the important role of coupling to phonons is confirmed. By comparing the measurements based on the $(^3\mathrm{He}, ^3\mathrm{He}'\gamma)$ and $(\gamma, \gamma')$ reactions, we discuss the physical properties of the radiative strength function measured for $^{208}\mathrm{Pb}$. For the neutron-rich $^{70}\mathrm{Ni}$ nucleus, predictions for the radiative strength function and the pygmy resonance are obtained using a partially self-consistent approach, which invokes the Skyrme forces in deriving the mean field, effective nucleon-nucleon interaction, and phonon characteristics.