Abstract
The low-energy level structure of the exotic Na isotopes has been investigated through -delayed spectroscopy. The isotones for are considered to belong to the “island of inversion” where intruder configurations dominate the ground state wave function. However, it is an open question as to where and how the transition from normal to intruder dominated configurations happens in an isotopic chain. The present work, which presents the first detailed spectroscopy of , clearly demonstrates that such a transition in the Na isotopes occurs between () and (), supporting the smaller shell gap in neutron-rich shell nuclei. The evidence for inverted shell structure is found in -decay branching ratios, intruder dominated spectroscopy of low-lying states, and shell model analysis.
- Received 16 November 2004
DOI:https://doi.org/10.1103/PhysRevLett.94.162501
©2005 American Physical Society