A dependence of the enhancement factor in energy-weighted sums for isovector giant resonances

We consider the energy weighted sums (EWS) for isovector giant dipole resonances (IVGDR) in finite nuclei within Landau kinetic theory. The dependence of both IVGDR energy, $E_{IVGDR}$, and the EWS enhancement factor, $\kappa (A)$, on the mass number $A$ occurs because of the boundary condition on the moving nuclear surface. The values of $E_{IVGDR}A^{1/3}$ and $\kappa (A)$ increase with $A$. The obtained value of the enhancement factor is about 10% for light nuclei and reaches approximately 20% for heavy nuclei. A fit of the enhancement factor to the proper experimental data provides a value for the isovector Landau amplitude of $F'_1\simeq 1.1$.