Structure of Sc 55 and development of the N=34 subshell closure

D. Steppenbeck, S. Takeuchi, N. Aoi, P. Doornenbal, M. Matsushita, H. Wang, H. Baba, S. Go, J. D. Holt, J. Lee, K. Matsui, S. Michimasa, T. Motobayashi, D. Nishimura, T. Otsuka, H. Sakurai, Y. Shiga, P. A. Söderström, S. R. Stroberg, T. SumikamaR. Taniuchi, J. A. Tostevin, Y. Utsuno, J. J. Valiente-Dobón, K. Yoneda

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The low-lying structure of Sc55 has been investigated using in-beam γ-ray spectroscopy with the Be9(Ti56,Sc55+γ)X one-proton removal and Be9(Sc55,Sc55+γ)X inelastic-scattering reactions at the RIKEN Radioactive Isotope Beam Factory. Transitions with energies of 572(4), 695(5), 1539(10), 1730(20), 1854(27), 2091(19), 2452(26), and 3241(39) keV are reported, and a level scheme has been constructed using γγ coincidence relationships and γ-ray relative intensities. The results are compared to large-scale shell-model calculations in the sd-pf model space, which account for positive-parity states from proton-hole cross-shell excitations, and to ab initio shell-model calculations from the in-medium similarity renormalization group that includes three-nucleon forces explicitly. The results of proton-removal reaction theory with the eikonal model approach were adopted to aid identification of positive-parity states in the level scheme; experimental counterparts of theoretical 1/21+ and 3/21+ states are suggested from measured decay patterns. The energy of the first 3/2- state, which is sensitive to the neutron shell gap at the Fermi surface, was determined. The result indicates a rapid weakening of the N=34 subshell closure in pf-shell nuclei at Z>20, even when only a single proton occupies the πf7/2 orbital.

Original languageEnglish
Article number064310
JournalPhysical Review C
Issue number6
Publication statusPublished - Dec 11 2017
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Nuclear and High Energy Physics


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