Manifestation of the Berry phase in the atomic nucleus $^{213}$Pb

TL;DR

This study observes how the Berry phase influences nuclear states in $^{213}$Pb, revealing the role of seniority quantum number conservation linked to particle-hole conjugation in semi-magic nuclei.

Contribution

It demonstrates the manifestation of the Berry phase in nuclear structure, connecting it to seniority quantum number conservation in semi-magic nuclei.

Findings

Identification of a new isomer in $^{213}$Pb

Evidence of seniority quantum number conservation

Link between Berry phase and nuclear state properties

Abstract

The neutron-rich $^{213}$Pb isotope was produced in the fragmentation of a primary 1 GeV $A$ $^{238}$U beam, separated in FRS in mass and atomic number, and then implanted for isomer decay $\gamma$-ray spectroscopy with the RISING setup at GSI. A newly observed isomer and its measured decay properties indicate that states in $^{213}$Pb are characterized by the seniority quantum number that counts the nucleons not in pairs coupled to angular momentum $J=0$. The conservation of seniority is a consequence of the Berry phase associated with particle-hole conjugation, which becomes gauge invariant and therefore observable in semi-magic nuclei where nucleons half-fill the valence shell. The $\gamma$-ray spectroscopic observables in $^{213}$Pb are thus found to be driven by two mechanisms, particle-hole conjugation and seniority conservation, which are intertwined through the Berry phase.