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

Abstract

The low-energy level structure of the exotic Na isotopes 28,29Na has been investigated through beta-delayed gamma 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 intruder dominated spectroscopy of low-lying states, beta-decay branching ratios and shell model analysis.

4 pages, 4 figures

References in corpus (2)

• Magic numbers in exotic nuclei and spin-isospin properties of {\it NN} interaction
• Onset of intruder ground state in exotic Na isotopes and evolution of the N=20 shell gap

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• Exploring the "Island of Inversion" by in-beam gamma-ray spectroscopy of the neutron-rich sodium isotopes 31,32,33Na
• Precision measurement of the electric quadrupole moment of 31Al and determination of the effective proton charge in the sd-shell
• Role of quadrupole deformation and continuum effects in the "island of inversion'' nuclei ${}^{28,29,31}$F
• Global nuclear structure aspects of tensor interaction
• Intruder configurations in ${}^{29}$Ne at the transition into the island of inversion: Detailed structure study of ${}^{28}$Ne
• Spectroscopy of ${}^{28}$Na: shell evolution toward the drip line
• Ab initio study of island of inversion in odd-$A$ nuclei: Structure of ${}^{31,33}$Mg
• Investigating nuclear density profiles to reveal particle-hole configurations in the island of inversion
• Coulomb breakup of neutron-rich ${}^{29,30}$Na isotopes near the island of inversion