Toroidal resonance: relation to pygmy mode, vortical properties and anomalous deformation splitting

TL;DR

This paper reviews recent advances in understanding the isoscalar toroidal dipole resonance (TDR), its relation to pygmy dipole strength, vortical nuclear motions, and the effects of nuclear deformation on TDR splitting.

Contribution

It provides a comprehensive analysis of the TDR's connection to pygmy modes, nuclear vorticity, and deformation effects, highlighting new insights into nuclear collective excitations.

Findings

Pygmy dipole strength can be viewed as local toroidal vortical motion.

TDR can serve as a measure of nuclear dipole vorticity.

Deformed nuclei exhibit an anomalous splitting of the TDR.

Abstract

We review a recent progress in investigation of the isoscalar toroidal dipole resonance (TDR). A possible relation of the TDR and low-energy dipole strength (also called a pygmy resonance) is analyzed. It is shown that the dipole strength in the pygmy region can by understood as a local manifestation of the collective vortical toroidal motion at the nuclear surface. Application of the TDR as a measure of the nuclear dipole vorticity is discussed. Finally, an anomalous splitting of the TDR in deformed nuclei is scrutinized.