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 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.

富集中子的²¹³ Pb同位素是通过将1 GeV A ²³⁸ U初级束破碎而产生的，质量和原子序数在FRS中分离，然后通过GSI的RISING装置植入，用于异构体衰变γ射线光谱分析。新近观察到的异构体及其测得的衰变特性表明，²¹³ Pb中的状态以能级数数为特征，该能级数计数不成对耦合于角动量的核子$Ĵ=0$。资历的保留是与粒子-空穴共轭相关的几何相的结果，在半魔术核中，核子半价化合了价态壳，这种几何相变得可见。因此发现²¹³ Pb中的γ射线光谱学观测结果是由两个机制驱动的：粒子-空穴共轭和资历守恒，这两个机制通过贝里相交织在一起。