Abstract
β-delayed one-proton emissions of Si22, the lightest nucleus with an isospin projection Tz=−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 Al22 are determined. Compared to the mirror β decay of O22, 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 s1/2 orbit that introduces explicitly the isospin-symmetry breaking force and describes the loosely bound nature of the wave functions of the s1/2 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 Al22. Our results, while supporting the proton-halo structure in Al22, might provide another means to identify halo nuclei.Received 27 February 2020Revised 26 July 2020Accepted 14 September 2020DOI:https://doi.org/10.1103/PhysRevLett.125.192503© 2020 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasBeta decayNuclear structure & decaysProton emissionNuclear Physics
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