Comment on "New formulas for the (-2) moment of the photoabsorption cross section, \sigma_(-2)"

Abstract

Empirical formulas for the second inverse moment of the photoabsorption cross sections in nuclei are discussed in J. N. Orce, Phys. Rev. C 91, 064602 (2015). In this Comment I point out that the experimental values used are systematically too small in heavy nuclei by about 10% because of the neglection of the E1 strength below the neutron threshold. Furthermore, combining recently deduced values of the polarizability in heavy and total photoabsorption data in light nuclei it is demonstrated that the mass number dependence of \sigma_(-2) is sensitive to the ratio of volume and surface coefficients of the symmetry energy and parameters different to the ones chosen by Orce may be better suited.