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Phys. Rev. C 77, 014316 (2008) [12 pages]

Single-neutron knockout from intermediate energy beams of 30,32Mg: Mapping the transition into the “island of inversion”

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J. R. Terry, B. A. Brown, C. M. Campbell, J. M. Cook, A. D. Davies, D.-C. Dinca, A. Gade, T. Glasmacher, P. G. Hansen, B. M. Sherrill, and H. Zwahlen
National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, USA and Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, USA

D. Bazin and K. Yoneda
National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, USA

J. A. Tostevin
Faculty of Engineering and Physical Sciences, University of Surrey, Guildford GU2 7XH, United Kingdom

T. Otsuka
Department of Physics and Center for Nuclear Study, University of Tokyo, Hongo, Tokyo 113-0033, Japan and RIKEN, Hirosawa, Wako-shi, Saitama 351-0198, Japan

Y. Utsuno
Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195, Japan

B. Pritychenko
Brookhaven National Laboratory, Upton, New York 11973-5000, USA

Received 5 March 2007; revised 15 October 2007; published 29 January 2008

The breakdown of the N=20 magic number in the so-called island of inversion around 32Mg is well established. Recently developed large-scale shell-model calculations suggest a transitional region between normal- and intruder-dominated nuclear ground states, thus modifying the boundary of the island of inversion. In particular, a dramatic change in single-particle structure is predicted between the ground states of 30Mg and 32Mg, with the latter consisting nearly purely of 2p-2h N=20 cross-shell configurations. Single-neutron knockout experiments on 30,32Mg projectiles have been performed. We report on a first direct observation of intruder configurations in the ground states of these very neutron-rich nuclei. Spectroscopic factors to low-lying negative-parity states in the knockout residues are deduced and compare well with shell-model predictions.

© 2008 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevC.77.014316
DOI:
10.1103/PhysRevC.77.014316
PACS:
21.10.Jx, 21.60.Cs, 25.70.Hi, 27.30.+t