Continuum quasiparticle linear response theory using the Skyrme functional for multipole responses of exotic nuclei

TL;DR

This paper introduces a new continuum QRPA formulation based on the Skyrme functional, accurately modeling multipole responses in exotic nuclei and analyzing the effects of velocity-dependent interactions.

Contribution

It presents a novel continuum QRPA approach derived directly from the Skyrme energy functional, including all velocity-dependent terms for better accuracy.

Findings

Energy-weighted sum rule is satisfied with good accuracy.

Velocity-dependent terms influence strength distribution and transition densities.

Method successfully models responses in exotic nuclei.

Abstract

We develop a new formulation of the continuum quasiparticle random phase approximation (QRPA) in which the residual interaction is derived directly from the Skyrme energy functional, keeping all the velocity dependent terms of the Skyrme effective interaction. Numerical analysis using the SkM$^*$ parameter set is performed for the isovector dipole and the isovector/isoscalar quadrupole responses in $^{20}$O and $^{54}$Ca. It is shown that the energy-weighted sum rule including the enhancement factors for the isovector responses is satisfied with good accuracy. We investigate also how the velocity dependent terms influence the strength distribution and the transition densities of the low-lying surface modes and the giant resonances.