Review of magnetic- and antimagnetic-rotational structures in nuclei

TL;DR

This review compiles and updates experimental data on magnetic- and antimagnetic-rotational nuclear structures, highlighting their features, configurations, and the need for further theoretical and experimental clarification.

Contribution

It provides a comprehensive update and critical analysis of experimental data on MR and AMR bands across many nuclei, emphasizing the role of proton magic numbers and identifying gaps in current data and models.

Findings

Many MR and AMR bands have tentative assignments due to lack of lifetime data.

Proton magic numbers appear to influence the occurrence of MR bands.

Theoretical models for many bands are still lacking or incomplete.

Abstract

This work is an update of the 2000 publication of magnetic-rotational bands by Amita et al. [1], followed by an unpublished update of 2006 [2], and reviews detailed experimental data extracted from original publications for 228 magnetic-rotational (MR or Shears) structures spread over 117 nuclides, and 40 antimagnetic-rotational (AMR) structures in 28 nuclei, with a brief commentary about each band. Many of these nuclei are located at or near the semi-magic nucleon numbers, mostly for protons. For example, 88 MR bands are currently known for the Pb (Z=82) nuclei, and 29 AMR band in Pd, Cd and In nuclei. It is interesting that the proton magic numbers appear to play a major role in the MR phenomenon, which seems less well understood. A brief discussion of the salient features of the MR and AMR bands and their theoretical interpretation has been presented in the present review. The tables contain gamma-ray energies, associated level energies with spins and parities, level lifetimes, B(M1), B(E2), and B(M1)/B(E2) ratios and probable spherical quasiparticle configurations. We find that many bands claimed in the literature as MR and AMR bands still have tentative assignments, as level lifetimes, thus B(M1) and B(E2) values, for a large number of MR and AMR bands, which can potentially provide critical criteria for firm identification of such structures, are lacking. Additionally, theoretical model calculations for many of these bands, which could provide insight for a better description of nuclear structure, are also lacking in literature. While this review is mainly based on original research articles, nuclear structure databases ENSDF [3], XUNDL [4], and NSR [5] have been consulted for completeness. The literature cut-off date March 31, 2025.