Manifestation of the Berry phase in the atomic nucleus 213Pb

J J Valiente-Dobón ,J J Valiente-Dobón ,M Pfützner,G Benzoni,S Leoni,S Leoni,M Doncel,I Kojouharov,S Lunardi,T Habermann,T Engert,S Klupp,R Menegazzo,A Gottardo,A Gottardo,J Benlliure,A Gadea,A Gadea,S Mandal,S Mandal,F Recchia,S Klupp,P Boutachkov,J Gerl,A Sharma,I Szarka,A Corsi,P Van Isacker,M Górska,Zs Podolyák,F Naqvi,D Mengoni,E Gregor,A Corsi,H Weick,N Goel,E Casarejos,O Wieland,C Nociforo,N Kurz,A Goasduff,D Bazzacco,S Lunardi,F Camera,F Camera,B Million,G De Angelis,G De Angelis,A Algora,A Algora,A Bracco,A Bracco,H Schaffner,Davinder Siwal ,P Strmeň ,S Piétri ,S Piétri ,B Sitár ,E Šahin ,A M Bruce ,A I Morales ,P M Walker ,S M Lenzi ,C A Ur ,P H Regan ,H J Wollersheim ,Dirk Rudolph ,C Domingo‐Pardo ,M L Cortés ,F C L Crespi ,D R Napoli ,A Procházka ,J Grębosz ,H Geißel

doi:10.1016/j.physletb.2021.136183

Abstract

The neutron-rich 213Pb isotope was produced in the fragmentation of a primary 1 GeV A238U beam, separated in FRS in mass and atomic number, and then implanted for isomer decay γ-ray spectroscopy with the RISING setup at GSI. A newly observed isomer and its measured decay properties indicate that states in 213Pb 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 a geometric phase associated with particle-hole conjugation, which becomes observable in semi-magic nuclei where nucleons half-fill the valence shell. The γ-ray spectroscopic observables in 213Pb are thus found to be driven by two mechanisms, particle-hole conjugation and seniority conservation, which are intertwined through a Berry phase.

Highlights

The neutron-rich 213Pb isotope was produced in the fragmentation of a primary 1 GeV A 238U beam, separated in FRS in mass and atomic number, and implanted for isomer decay γ -ray spectroscopy with the RISING setup at GSI
A newly observed isomer and its measured decay properties indicate that states in 213Pb are characterized by the seniority quantum number that counts the nucleons not in pairs coupled to angular momentum J = 0
The γ -ray spectroscopic observables in 213Pb are found to be driven by two mechanisms, particle-hole conjugation and seniority conservation, which are intertwined through a Berry phase

Summary

Contents lists available at ScienceDirect

The conservation of seniority is a consequence of a geometric phase associated with particle-hole conjugation, which becomes observable in semi-magic nuclei where nucleons half-fill the valence shell. The phase is normally without any observable consequence except if either neutrons or protons half-fill a valence single- j shell, in which case the original and transformed state are the same. A J π = 21/2+ seniority isomer with a half-life of 42 ns, originating from the maximum coupling of three 1g9/2 neutrons, is known [36] in 211Pb. Its decay to the 9/2+ ground state is identified in a sequence of three γ -ray transitions, 137, 322, and 734 keV, feeding successively the 17/2+, 13/2+, and 9/2+ levels. The 1g9/2 shell is not isolated in energy, it is found to carry the dominant component of the wave function of low-energy states

We note that the KLS interaction and the truncation from

Findings

This finding agrees qualitatively with the isomeric character of the