Abstract
-delayed one-proton emissions of , the lightest nucleus with an isospin projection , are studied with a silicon array surrounded by high-purity germanium detectors. Properties of -decay branches and the reduced transition probabilities for the transitions to the low-lying states of are determined. Compared to the mirror decay of , the largest value of mirror asymmetry in low-lying states by far, with , is found in the transition to the first excited state. Shell-model calculation with isospin-nonconserving forces, including the , , 3 interaction related to the orbit that introduces explicitly the isospin-symmetry breaking force and describes the loosely bound nature of the wave functions of the orbit, can reproduce the observed data well and consistently explain the observation that a large value occurs for the first but not for the second excited state of . Our results, while supporting the proton-halo structure in , might provide another means to identify halo nuclei.
- Received 27 February 2020
- Revised 26 July 2020
- Accepted 14 September 2020
DOI:https://doi.org/10.1103/PhysRevLett.125.192503
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