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Phys. Rev. Lett. 94, 162501 (2005) [4 pages]

29Na: Defining the Edge of the Island of Inversion for Z=11

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Vandana Tripathi1, S. L. Tabor1, P. F. Mantica2,3, C. R. Hoffman1, M. Wiedeking1, A. D. Davies2,4, S. N. Liddick2,3, W. F. Mueller2, T. Otsuka5,6, A. Stolz2, B. E. Tomlin2,3, Y. Utsuno7, and A. Volya1
1Department of Physics, Florida State University, Tallahassee, Florida 32306, USA
2National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, USA
3Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, USA
4Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, USA
5Department of Physics and Center for Nuclear Study, University of Tokyo, Hongo, Tokyo 113-0033, Japan
6RIKEN, Hirosawa, Wako-shi, Saitama 351-0198, Japan
7Japan Atomic Energy Research Institute, Tokai, Ibaraki 319-1195, Japan

Received 16 November 2004; published 25 April 2005

The low-energy level structure of the exotic Na isotopes 28,29Na has been investigated through β-delayed γ spectroscopy. The N=20 isotones for Z=10–12 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 28,29Na, clearly demonstrates that such a transition in the Na isotopes occurs between 28Na (N=17) and 29Na (N=18), supporting the smaller N=20 shell gap in neutron-rich sd shell nuclei. The evidence for inverted shell structure is found in β-decay branching ratios, intruder dominated spectroscopy of low-lying states, and shell model analysis.


©2005 The American Physical Society

URL: http://link.aps.org/doi/10.1103/PhysRevLett.94.162501
DOI: 10.1103/PhysRevLett.94.162501
PACS: 23.40.-s, 21.60.Cs, 23.20.Lv, 27.30.+t

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