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Empirical drops in ground-state nuclear polarizabilities indicate deviations from the effect of giant dipole resonances and may reveal the presence of shell effects in semi-magic nuclei with neutron magic numbers $N=50$, 82 and 126. Similar drops of polarizability in the quasi-continuum of nuclei with, or close to, magic numbers $N=28$, 50 and 82, could reflect the continuing influence of shell closures up to the nucleon separation energy. These findings open a new avenue to investigating magic numbers at high-excitation energies and strongly support recent large-scale shell-model calculations in the quasi-continuum region, which describe the origin of the low-energy enhancement of the photon strength function as induced paramagnetism. The nuclear-structure dependence of the photon-strength function asserts the generalized Brink-Axel hypothesis as more universal than originally expected.

This is a Reply to a Comment on my paper: New formulas for the (-2) moment of the photo-absorption cross section, sigma-2., Comment: 2 pages, 1 figure

Two new formulae for the $(-2)$ moment of the photo-absorption cross section, $\sigma_{_{-2}}$, have been determined, respectively, from the 1988 compilation of Dietrich and Berman and a mass-dependent symmetry energy coefficient, $a_{sym}(A)$. The data for $A\gtrsim50$ follow, with a {\small $RMS$} deviation of 6\%, the power-law $\sigma_{_{-2}}=2.4 A^{5/3}$$\mu$b/MeV, which is in agreement with Migdal's calculation of $\sigma_{_{-2}}=2.25A^{5/3}$$\mu$b/MeV based on the hydrodynamic model and the $\sigma_{_{-2}}$ sum rule. The additional inclusion of $a_{sym}(A)$ provides a deeper insight to the nuclear polarization of $A\geqq10$ nuclei., Comment: 4 pages, 4 figures