Isovector response and energy-weighted sums in hot nuclei

TL;DR

This paper studies the temperature effects on the isovector giant dipole resonance in hot nuclei using kinetic theory, revealing how energy centroids and sum rules vary with temperature and nuclear size.

Contribution

It introduces a temperature-dependent analysis of isovector response functions and energy-weighted sums, incorporating Fermi surface distortion effects and surface vibrations.

Findings

Centroid energy $E_3$ weakly varies with temperature.

Enhancement factor for $m_1$ is only slightly affected by temperature.

Good agreement with experimental data on $A$-dependence of IVGDR energy.

Abstract

We investigate the collective response function and the energy-weighted sums (EWS) $m_k$ for isovector mode in hot nuclei. The approach is based on the collisional kinetic theory and takes into consideration the temperature and the relaxation effects. We have evaluated the temperature dependence of the adiabatic, $E_1=\sqrt{m_1/m_{-1}}$, and scaling, $E_3=\sqrt{m_3/m_1}$, energy centroids of the isovector giant dipole resonances (IVGDR). The centroid energy $E_3$ is significantly influenced by the Fermi surface distortion effects and, in contrast to the isoscalar mode, shows much weaker variation with temperature. Taking into account a connection between the isovector sound mode and the corresponding surface vibrations we have established the $A$-dependence of the IVGDR centroid energy which is in a good agreement with experimental data. We have shown that the enhancement factor for the "model independent" sum $m_1$ is only slightly sensitive to the temperature change.