Spectroscopic Criteria for Identification of Nuclear Tetrahedral and Octahedral Symmetries: Illustration on a Rare Earth Nucleus

TL;DR

This paper develops spectroscopic criteria to identify nuclear tetrahedral and octahedral symmetries, illustrating their potential realization in a rare earth nucleus through advanced theoretical calculations and analysis of experimental data.

Contribution

It introduces a novel set of spectroscopic criteria for detecting exotic nuclear symmetries, supported by comprehensive theoretical modeling and application to experimental observations.

Findings

Identification criteria for tetrahedral and octahedral symmetries in nuclei.

Existence of exotic rotational bands with unique properties.

Implications for nuclear shape-isomers and astrophysical nucleosynthesis.

Abstract

We formulate criteria for identification of the nuclear tetrahedral and octahedral symmetries and illustrate for the first time their possible realization in a Rare Earth nucleus 152Sm. We use realistic nuclear mean-field theory calculations with the phenomenological macroscopic-microscopic method, the Gogny-Hartree-Fock-Bogoliubov approach and the general point-group theory considerations to guide the experimental identification method as illustrated on published experimental data. Following group-theory the examined symmetries imply the existence of exotic rotational bands on whose properties the spectroscopic identification criteria are based. These bands may contain simultaneously states of even and odd spins, of both parities and parity doublets at well defined spins. In the exact-symmetry limit those bands involve no E2-transitions. We show that coexistence of tetrahedral and octahedral deformations is essential when calculating the corresponding energy minima and surrounding barriers and that it has a characteristic impact on the rotational bands. The symmetries in question imply the existence of long-lived shape-isomers and, possibly, new waiting point nuclei -- impacting the nucleosynthesis processes in astrophysics -- and an existence of 16-fold degenerate particle-hole excitations. Specifically designed experiments which aim at strengthening the identification arguments are briefly discussed.