Nuclear isomers, seniority and particle-hole conjugation
Dr. Piet Van Isacker
GANIL, France
Seniority refers to the number of nucleons that are not in pairs coupled to angular momentum J=0. It is a symmetry associated with the pairing interaction and, more generally, it is a quantum number approximately conserved for a general interaction between either neutrons or protons. In this talk I review the conditions for the conservation of seniority and show that they are a manifestation of particle-hole symmetry.
Seniority gives rise to selection rules in the electromagnetic decay in nuclei, which may lead to the formation of isomers. Examples of seniority isomers are discussed in the nickel and lead isotopes, and in the N=50, 82 and 126 isotones. The seniority scheme predicts relations between B(E2) values in even-even and odd-mass nuclei that are different from those of the particle-core coupling model. The question of (state-dependent) effective E2 charges in the shell model is also discussed.
Hosted by Prof. Aprahamian