Individual Low-Energy Toroidal Dipole State in ^{24}Mg

Area of Science:

• Nuclear Physics
• Quantum Mechanics
• Atomic Physics

Background:

• Low-energy dipole excitations in atomic nuclei are crucial for understanding nuclear structure.
• Toroidal states (TS) represent a unique excitation mode with potential experimental signatures.
• Skyrme quasiparticle random phase approximation (QRPA) is a theoretical framework for nuclear structure calculations.

Purpose of the Study:

• To investigate low-energy dipole excitations in ^{24}Mg.
• To identify and characterize vortical toroidal states (TS) in deformed nuclei.
• To explore the relationship between TS and nuclear cluster structure.

Main Methods:

• Utilizing the Skyrme quasiparticle random phase approximation (QRPA) for axial nuclei.
• Employing the SLy6 Skyrme force parametrization for calculations.
• Analyzing spectroscopic properties and comparing results across different Skyrme parametrizations (SLy6, SVbas, SkM*).

Main Results:

• Identified the lowest I^{π}K=1^{-}1 excitation in ^{24}Mg as a vortical toroidal state (TS) at 7.92 MeV.
• The TS is a vortex-antivortex realization of Hill's vortex within a deformed axial confinement.
• The TS's low energy is attributed to the significant prolate axial deformation in ^{24}Mg.
• This individual TS is experimentally more accessible than toroidal dipole resonances.

Conclusions:

• The study confirms the existence of an individual vortical toroidal state (TS) in ^{24}Mg.
• This TS provides a unique experimental probe for nuclear flow in highly prolate light nuclei.
• Similar toroidal states may exist in other deformed light nuclei, offering new avenues for nuclear reaction studies.