How Robust is the $N = 34$ Subshell Closure? First Spectroscopy of $^{52}$Ar

H.N. Liu (1) , A. Obertelli (1) , P. Doornenbal , C.A. Bertulani , G. Hagen , J.D. Holt , G.R. Jansen , T.D. Morris , A. Schwenk , R. Stroberg , N.L. Achouri (2) , H. Baba , F. Browne , D. Calvet (1) , F. Château (1) , S. Chen , N. Chiga , A. Corsi (1) , M.L. Cortés , A. Delbart (1) , J.-M. Gheller (1) , A. Giganon (1) , A. Gillibert (1) , C. Hilaire (1) , T. Isobe , T. Kobayashi , Y. Kubota , V. Lapoux (1) , T. Motobayashi , I. Murray (2) , H. Otsu , V. Panin , N. Paul (1) , W. Rodriguez , H. Sakurai , M. Sasano , D. Steppenbeck , L. Stuhl , Y.L. Sun (1) , Y. Togano , T. Uesaka , K. Wimmer , K. Yoneda , O. Aktas , T. Aumann , L.X. Chung , F. Flavigny (2) , S. Franchoo (2) , I. Gašparić , R.-B. Gerst , J. Gibelin (3) , K.I. Hahn , D. Kim , T. Koiwai , Y. Kondo , P. Koseoglou , J. Lee , C. Lehr , B.D. Linh , T. Lokotko , M. Maccormick (2) , K. Moschner , T. Nakamura , S.Y. Park , D. Rossi , E. Sahin , D. Sohler , P.-A. Söderström , S. Takeuchi , H. Törnqvist , V. Vaquero , V. Wagner , S. Wang , V. Werner , X. Xu , H. Yamada , D. Yan , Z. Yang , M. Yasuda , L. Zanetti

1 IRFU - Institut de Recherches sur les lois Fondamentales de l'Univers
2 IPNO - Institut de Physique Nucléaire d'Orsay
3 LPCC - Laboratoire de physique corpusculaire de Caen

The first γ-ray spectroscopy of Ar52, with the neutron number N=34, was measured using the K53(p,2p) one-proton removal reaction at ∼210  MeV/u at the RIBF facility. The 21+ excitation energy is found at 1656(18) keV, the highest among the Ar isotopes with N>20. This result is the first experimental signature of the persistence of the N=34 subshell closure beyond Ca54, i.e., below the magic proton number Z=20. Shell-model calculations with phenomenological and chiral-effective-field-theory interactions both reproduce the measured 21+ systematics of neutron-rich Ar isotopes, and support a N=34 subshell closure in Ar52.

Mots clés: Nuclear Physics

Domaines: Physique Nucléaire Expérimentale [nucl-ex]; Physique Nucléaire Théorique [nucl-th]

H.N. Liu, A. Obertelli, P. Doornenbal, C.A. Bertulani, G. Hagen, et al.. How Robust is the $N = 34$ Subshell Closure? First Spectroscopy of $^{52}$Ar. Physical Review Letters, 2019, 122 (7), pp.072502. ⟨10.1103/PhysRevLett.122.072502⟩. ⟨hal-01952664⟩