Large Isospin Asymmetry in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mmultiscripts><mml:mrow><mml:mi>Si</mml:mi></mml:mrow><mml:mprescripts/><mml:none/><mml:mrow><mml:mn>22</mml:mn></mml:mrow></mml:mmultiscripts></mml:mrow><mml:mo>/</mml:mo><mml:mrow><mml:mmultiscripts><mml:mrow><mml:mi mathvariant="normal">O</mml:mi></mml:mrow><mml:mprescripts/><mml:none/><mml:mrow><mml:mn>22</mml:mn></mml:mrow></mml:mmultiscripts></mml:mrow></mml:math> Mirror Gamow-Teller Transitions Reveals the Halo Structure of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mmultiscripts><mml:mrow><mml:mi>Al</mml:mi></mml:mrow><mml:mprescripts/><mml:none/><mml:mrow><mml:mn>22</mml:mn></mml:mrow></mml:mmultiscripts></mml:mrow></mml:math>
J. Lee, Xiangxiang Xu, Kazunari Kaneko, Y. Sun, C. J. Lin, L. J. Sun, Pengfei Liang, Z. H. Li, Jian-Rong Li, H. y. Wu, Deqing Fang, J. S. Wang, Y. Y. Yang, Cenxi Yuan, Y. H. Lam, Y. T. Wang, K. Wang, J. G. Wang, J. B., J. J. Liu, P. J. Li, Qiong Zhao, L. Yang, N. R., D. X. Wang, F. P. Zhong, Shi-Yi Zhong, F. Yang, H. M. Jia, Peiwei Wen, Min Pan, H. L. Zang, X. Wang, C. Wu, D. W. Luo, H. W. Wang, C. Li, C. Z. Shi, Maowu Nie, X. F. Li, H. Li, P. Ma, Q. Hu, G. Z. Shi, S. Jin, M. R. Huang, Zhiyong Bai, Yongjie Zhou, W. H., F. F. Duan, Shichao Jin, Q. Gao, Xin‐Hui Zhou, Zhengguo Hu, M. Wang, Maohang Liu, Renmiao Chen, X. W.
Abstract
β-delayed one-proton emissions of ^{22}Si, the lightest nucleus with an isospin projection T_{z}=-3, are studied with a silicon array surrounded by high-purity germanium detectors. Properties of β-decay branches and the reduced transition probabilities for the transitions to the low-lying states of ^{22}Al are determined. Compared to the mirror β decay of ^{22}O, the largest value of mirror asymmetry in low-lying states by far, with δ=209(96), is found in the transition to the first 1^{+} excited state. Shell-model calculation with isospin-nonconserving forces, including the T=1, J=2, 3 interaction related to the s_{1/2} orbit that introduces explicitly the isospin-symmetry breaking force and describes the loosely bound nature of the wave functions of the s_{1/2} orbit, can reproduce the observed data well and consistently explain the observation that a large δ value occurs for the first but not for the second 1^{+} excited state of ^{22}Al. Our results, while supporting the proton-halo structure in ^{22}Al, might provide another means to identify halo nuclei.