Observation of the near-threshold intruder <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msup><mml:mn>0</mml:mn><mml:mo>−</mml:mo></mml:msup></mml:math> resonance in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mmultiscripts><mml:mi>Be</mml:mi><mml:mprescripts/><mml:none/><mml:mn>12</mml:mn></mml:mmultiscripts></mml:math>
J. Chen, S. M. Wang, H. T. Fortune, J. L. Lou, Yanlin Ye, Zhen Li, N. Michel, J. G. Li, Cenxi Yuan, Y. C. Ge, Q. T. Li, H. Hua, D. Jiang, X. F. Yang, D. Y. Pang, F. R. Xu, W. Zuo, J. C. Pei, J. Li, Weichun Jiang, Y. L. Sun, H. L. Zang, N. Aoi, H. J. Ong, E. Ideguchi, Y. Ayyad, K. Hatanaka, D. T. Tran, D. Bazin, J. Lee, Y.N. Zhang, J. Wu, Hongna Liu, Chao Wen, T. Yamamoto, M. Tanaka, T. Suzuki
Abstract
A resonant state at $3.{21}_{\ensuremath{-}0.04}^{+0.12}\phantom{\rule{4pt}{0ex}}\mathrm{MeV}$, located just above the one-neutron separation threshold, was observed for the first time in $^{12}\mathrm{Be}$ from the $^{11}\mathrm{Be}(d,p)^{12}\mathrm{Be}$ one-neutron transfer reaction in inverse kinematics. This state is assigned a spin-parity of ${0}^{\ensuremath{-}}$ according to the systematics of the level scheme of the $N=8$ isotones and decay-width analysis. Gamow coupled-channel and Gamow shell-model calculations show the importance of the continuum coupling, which dramatically influences the excitation energy and ordering of low-lying states. Various exotic structures associated with cross-shell intruding configurations in $^{12}\mathrm{Be}$ and in its isotonic nucleus $^{11}\mathrm{Li}$ are comparably discussed.