Low-Lying Structure of Ar 50 and the N=32 Subshell Closure

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

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The low-lying structure of the neutron-rich nucleus Ar50 has been investigated at the Radioactive Isotope Beam Factory using in-beam γ-ray spectroscopy with Be9(Ca54,Ar50+γ)X, Be9(Sc55,Ar50+γ)X, and Be9(Ti56,Ar50+γ)X multinucleon removal reactions at ∼220MeV/u. A γ-ray peak at 1178(18) keV is reported and assigned as the transition from the first 2+ state to the 0+ ground state. A weaker, tentative line at 1582(38) keV is suggested as the 41+→21+ transition. The experimental results are compared to large-scale shell-model calculations performed in the sdpf model space using the SDPF-MU effective interaction with modifications based on recent experimental data for exotic calcium and potassium isotopes. The modified Hamiltonian provides a satisfactory description of the new experimental results for Ar50 and, more generally, reproduces the energy systematics of low-lying states in neutron-rich Ar isotopes rather well. The shell-model calculations indicate that the N=32 subshell gap in Ar50 is similar in magnitude to those in Ca52 and Ti54 and, notably, predict an N=34 subshell closure in Ar52 that is larger than the one recently reported in Ca54.

Original languageEnglish
Article number252501
JournalPhysical review letters
Issue number25
Publication statusPublished - Jun 25 2015
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Physics and Astronomy(all)


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