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

TL;DR

This paper critiques previous empirical formulas for the second inverse moment of photoabsorption cross sections, highlighting systematic underestimations in experimental data and proposing that the mass dependence is sensitive to symmetry energy parameters.

Contribution

It identifies systematic errors in experimental data and suggests alternative parameters for better modeling of  moments in nuclei.

Findings

Experimental values are underestimated by ~10% in heavy nuclei.

The mass dependence of  is sensitive to symmetry energy ratios.

Alternative parameters may improve the empirical formulas.

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.