Toroidal dipole mode in nuclei

TL;DR

The paper surveys the toroidal dipole mode (TDM) in nuclei and discusses its mean-field origin and general presence across nuclear systems. It emphasizes a Chandrasekhar-Moffat style current decomposition into irrotational, magnetic, and toroidal parts, noting that the toroidal component is transversal and decoupled from the continuity equation. In Ni-58, fully self-consistent QRPA calculations with a Skyrme interaction reproduce low-energy isoscalar toroidal dipole states and explain enhanced transversal form factors in (e,e') experiments, placing these states below the GDR. The discussion addresses limitations and the potential role of complex configurations, with broader implications for interpreting pygmy dipole resonance and for developing experimental methods to excite and identify electric vortical modes in nuclei.

Abstract

A short review on the toroidal dipole mode (TDM) in nuclei is done. The appearance of TDM in nuclei is justified. The experimental manifestation of TDM in (e,e') reaction in 58Ni is shortly reported. The relation of TDM and pygmy E1 resonance is discussed.

Figures (3)

• Figure 1: (a) Schematic picture of TDM. (b) Isoscalar (T=0) TDM in $^{208}$Pbrep13.
• Figure 2:
• Figure 3: The squared TFF computed with Skyrme parametrization SVmas10 for QRPA states at 8.26 and 9.85 MeV, as compared with experimental data Reitz for the states at 8.24 and 10.04 MeV.