title: Extension of the N=40 Island of Inversion towards N=50: Spectroscopy of (66)Cr, (70,72)Fe.
abstract: We report on the measurement of the first 2(+) and 4(+) states of (66)Cr and (70,72)Fe via in-beam γ-ray spectroscopy. The nuclei of interest were produced by (p,2p) reactions at incident energies of 260  MeV/nucleon. The experiment was performed at the Radioactive Isotope Beam Factory, RIKEN, using the DALI 2γ-ray detector array and the novel MINOS device, a thick liquid hydrogen target combined with a vertex tracker. A low-energy plateau of 2(1)(+) and 4(1)(+) energies as a function of the neutron number was observed for N≥38 and N≥40 for even-even Cr and Fe isotopes, respectively. State-of-the-art shell model calculations with a modified Lenzi-Nowacki-Poves-Sieja (LNPS) interaction in the pfg(9/2)d(5/2) valence space reproduce the observations. Interpretation within the shell model shows an extension of the island of inversion at N=40 for more neutron-rich isotopes towards N=50.
authors.affiliation: CEA, Centre de Saclay, IRFU, F-91191 Gif-sur-Yvette, France.|RIKEN Nishina Center, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.
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authors.affiliation: Institut für Kernphysik, Technische Universität Darmstadt, 64289 Darmstadt, Germany.
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authors.affiliation: CEA, Centre de Saclay, IRFU, F-91191 Gif-sur-Yvette, France.|RIKEN Nishina Center, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.
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authors.affiliation: Institut für Kernphysik, Technische Universität Darmstadt, 64289 Darmstadt, Germany.|WNSL, Yale University, P.O. Box 208120, New Haven, Connecticut 06520, USA.
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authors.affiliation: RIKEN Nishina Center, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.
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authors.affiliation: RIKEN Nishina Center, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.
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authors.affiliation: RIKEN Nishina Center, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.|Department of Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033, Japan.
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