Eur. Phys. J. A (2006) 27: 257-267
https://doi.org/10.1140/epja/i2006-08-040-7

Nuclear Physics in Astrophysics II

Nuclear structure far off stability --Implications for nuclear astrophysics

¹ GSI, D-64291, Darmstadt, Germany
² University of Sofia, Sofia, Bulgaria
³ Department of Physics and Astronomy, University of Tennessee, 37996, Knoxville, TN, USA
⁴ ISV, Uppsala University, Nyköping, Sweden
⁵ RRC Kurchatov Institute, RU-123481, Moscow, Russia
⁶ Katholieke Universiteit Leuven, Leuven, Belgium

^* e-mail: h.grawe@gsi.de

Received: 20 June 2005
Accepted: 20 December 2005
Published online: 15 March 2006

Abstract

The single-particle structure and shell gap of ¹⁰⁰Sn as inferred from previous in-beam γ-ray spectroscopy has been confirmed in recent studies of seniority and spin-gap isomers by γγ, βγ, βpγ, pγ and 2pγ spectroscopy. The results for ^{94, 95}Ag, ⁹⁸Cd and its N = 50 isotones ⁹⁶Pd and ⁹⁴Ru stress the importance of large-scale shell model calculations employing realistic interactions for the isomerism, np-nh excitations, seniority mixing and E2 polarisation of the ¹⁰⁰Sn core. The strong monopole interaction of the Δl = 0, 1 spin/isospin-flip partners πg _9/2- νg _7/2 along the N = 50 isotones and the πf _5/2- νg _9/2 pair of nucleons along the Z = 28 Ni isotopes are decisive for the evolution of the shell structure towards ¹⁰⁰Sn and ⁷⁸Ni. It can be traced back to the tensor force in the effective nucleon-nucleon interaction and provides a straightforward explanation for new shells in neutron-rich light nuclei, implying qualitative predictions for new N = 32, 34 subshells in Ca isotopes, persistence of the ⁷⁸Ni proton and neutron shell gaps and non-equivalence of the g _9/2 valence mirror Ni isotopes and N = 50 isotones. This is corroborated by recent experimental data on ^{56, 58}Cr and ^70-76Ni. The implication of monopole driven shell evolution for apparent spin-orbit splitting towards N ≫ Z and structure along the astrophysical r-path between N = 50 and N = 82 is discussed.