DOE OSTI Β· 3377110
π = 8 Shell Breaking in 12 Be from a Single-Particle Perspective
Abstract
Experimental observations of the low-lying states in 12 Be and their accurate modeling play an essential role in understanding the disappearance of the π = 8 magic number. Long-standing experimental ambiguities have been clarified using an one-neutron adding (π, π) reaction on 11 Be using the ISOLDE Solenoidal Spectrometer at CERNβs HIE-ISOLDE facility. The single-particle energies of 1β’π 1/2 , 0β’π 5/2 , and 0β’π 1/2 orbitals in 12 Be have been determined from the extracted spectroscopic factors. A significant reduction between the separation of 1β’π 1/2 and 0β’π 1/2 orbitals is found in comparison with the carbon isotones, highlighting the breakdown of the π = 8 shell. These observations serve as an important test of different effects incorporated in theoretical models. It is found that two synergistic mechanisms, core deformation and weak binding, are responsible for the π = 8 shell breaking and the exotic near-threshold phenomena observed in 12 Be, including the narrow unnatural-parity resonance $0^{-}_1$ and the possible halolike nature of the $0^+_2$ isomer.
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Chen, Jie [Southern University of Science and Technology; Argonne National Laboratory] (ORCID:0000000343366726), Kay, B. P. [Argonne National Laboratory] (ORCID:0000000186750731), Sharp, D. K. [University of Manchester], Gaffney, L. P. [University of Liverpool], Freeman, S. J. [University of Manchester; CERN], Wang, S. M. [Fudan University; Fudan University], Li, J. G. [Institute of Modern Physics; University of Chinese Academy of Sciences; Institute of Modern Physics], MacGregor, P. T. [University of Manchester; CERN], Hoffman, C. R. [Argonne National Laboratory], Ayyad, Y. [Universidade de Santiago de Compostela], Butler, P. A. [University of Liverpool], Carollo, S. [Universit degli Studi di Padova; Istituto Nazionale di Fisica Nucleare (INFN)], Ceulemans, A. [KU Leuven], Clarke, D. J. [University of Manchester], Dolan, A. J. [University of Liverpool], Everett, C. [University of Liverpool], Favier, Z. [CERN], Garrett, K. [University of Manchester], Geng, J. [Lanzhou University], Jayatissa, H. [Argonne National Laboratory], Labiche, M. [Daresbury], Lazarus, I. [Daresbury], Liu, W. P. [Southern University of Science and Technology], Niu, Y. F. [Lanzhou University], Olaizola, B. [CERN; Instituto de Estructura de la Materia], Ojala, J. [University of Liverpool], Page, C. A. A. [University of York; CERN], Page, R. D. [University of Liverpool], Poleshchuk, O. [KU Leuven], Raabe, R. [KU Leuven], Xie, M. R. [Institute of Modern Physics; University of Chinese Academy of Sciences], Yuan, C. X. [Sun Yat-Sen University], Yue, Z. [University of York; CERN], Zhang, Y. N. [Sun Yat-Sen University]. 2026-06-02. π = 8 Shell Breaking in 12 Be from a Single-Particle Perspective. https://doi.org/10.1103/3vts-dwst
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