Skyrme-Hartree-Fock-BCS approach to $^{229m}$Th and neighboring nuclei

TL;DR

This paper uses a self-consistent Skyrme Hartree-Fock plus BCS model to explore the microscopic origin of the $^{229m}$Th isomer, successfully reproducing its key properties and providing insights into related observables and neighboring nuclei.

Contribution

It demonstrates that the Skyrme-Hartree-Fock-BCS approach can accurately reproduce the $^{229m}$Th isomer's properties without special adjustments, offering a microscopic basis for understanding low-energy nuclear isomers.

Findings

Reproduces the isomer's spin and parity accurately.

Provides estimates for quadrupole, octupole moments, and magnetic dipole moments.

Discusses prediction of M1 isomer transition probability.

Abstract

The microscopic origin of the $^{229m}$Th isomer and its possible manifestation also in neighboring nuclei is explored within a selfconsistent Skyrme Hartree-Fock plus Bardeen-Cooper-Schrieffer approach. By using the well established SIII Skyrme parametrization, without any special adjustments related to low-energy isomer, the single-particle spectrum provided by the model reproduces the correct isomer $K^{\pi}=3/2^{+}$ spin and parity, and the relative proximity of the isomeric state to the $K^{\pi}=5/2^{+}$ ground state, yet on the keV scale. We show that this approach may provide microscopic estimates for some related observables, such as the quadrupole and octupole moments, deformation parameters as well as magnetic dipole moments. Its ability to provide a prediction for the M1 isomer transition probability is discussed. The obtained $^{229}$Th single-particle structure is compared with that provided by calculations in neighbouring actinide isotopes and isotones, allowing us to assess the more general role of the considered mechanism for the formation of low-energy isomers.