title: Low-Lying Structure of (50)Ar and the N=32 Subshell Closure.
abstract: The low-lying structure of the neutron-rich nucleus (50)Ar has been investigated at the Radioactive Isotope Beam Factory using in-beam γ-ray spectroscopy with (9)Be((54)Ca,(50)Ar+γ)X, (9)Be((55)Sc,(50)Ar+γ)X, and (9)Be((56)Ti,(50)Ar+γ)X multinucleon removal reactions at ∼220  MeV/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 4(1)(+)→2(1)(+) 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 (50)Ar 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 (50)Ar is similar in magnitude to those in (52)Ca and (54)Ti and, notably, predict an N=34 subshell closure in (52)Ar that is larger than the one recently reported in (54)Ca.
authors.affiliation: Center for Nuclear Study, University of Tokyo, Hongo, Bunkyo, Tokyo 113-0033, Japan.
authors.forename: D
authors.initials: D
authors.lastname: Steppenbeck
authors.affiliation: RIKEN Nishina Center, 2-1, Hirosawa, Wako, Saitama 351-0198, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Takeuchi
authors.affiliation: Research Center for Nuclear Physics, University of Osaka, Ibaraki, Osaka 567-0047, Japan.
authors.forename: N
authors.initials: N
authors.lastname: Aoi
authors.affiliation: RIKEN Nishina Center, 2-1, Hirosawa, Wako, Saitama 351-0198, Japan.
authors.forename: P
authors.initials: P
authors.lastname: Doornenbal
authors.affiliation: Center for Nuclear Study, University of Tokyo, Hongo, Bunkyo, Tokyo 113-0033, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Matsushita
authors.affiliation: RIKEN Nishina Center, 2-1, Hirosawa, Wako, Saitama 351-0198, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Wang
authors.affiliation: Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Utsuno
authors.affiliation: RIKEN Nishina Center, 2-1, Hirosawa, Wako, Saitama 351-0198, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Baba
authors.affiliation: Center for Nuclear Study, University of Tokyo, Hongo, Bunkyo, Tokyo 113-0033, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Go
authors.affiliation: RIKEN Nishina Center, 2-1, Hirosawa, Wako, Saitama 351-0198, Japan.
authors.forename: J
authors.initials: J
authors.lastname: Lee
authors.affiliation: Department of Physics, University of Tokyo, Hongo, Bunkyo, Tokyo 113-0033, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Matsui
authors.affiliation: Center for Nuclear Study, University of Tokyo, Hongo, Bunkyo, Tokyo 113-0033, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Michimasa
authors.affiliation: RIKEN Nishina Center, 2-1, Hirosawa, Wako, Saitama 351-0198, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Motobayashi
authors.affiliation: Department of Physics, Tokyo University of Science, Noda, Chiba 278-8510, Japan.
authors.forename: D
authors.initials: D
authors.lastname: Nishimura
authors.affiliation: Center for Nuclear Study, University of Tokyo, Hongo, Bunkyo, Tokyo 113-0033, Japan.|Department of Physics, University of Tokyo, Hongo, Bunkyo, Tokyo 113-0033, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Otsuka
authors.affiliation: RIKEN Nishina Center, 2-1, Hirosawa, Wako, Saitama 351-0198, Japan.|Department of Physics, University of Tokyo, Hongo, Bunkyo, Tokyo 113-0033, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Sakurai
authors.affiliation: Department of Physics, Rikkyo University, Toshima, Tokyo 171-8501, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Shiga
authors.affiliation: Center for Nuclear Study, University of Tokyo, Hongo, Bunkyo, Tokyo 113-0033, Japan.
authors.forename: N
authors.initials: N
authors.lastname: Shimizu
authors.affiliation: RIKEN Nishina Center, 2-1, Hirosawa, Wako, Saitama 351-0198, Japan.
authors.forename: P-A
authors.initials: PA
authors.lastname: Söderström
authors.affiliation: Department of Physics, Tohoku University, Sendai, Miyagi 980-8578, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Sumikama
authors.affiliation: Department of Physics, University of Tokyo, Hongo, Bunkyo, Tokyo 113-0033, Japan.
authors.forename: R
authors.initials: R
authors.lastname: Taniuchi
authors.affiliation: Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Legnaro, Legnaro 35020, Italy.
authors.forename: J J
authors.initials: JJ
authors.lastname: Valiente-Dobón
authors.affiliation: RIKEN Nishina Center, 2-1, Hirosawa, Wako, Saitama 351-0198, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Yoneda