Abstract
decay of proton-rich nuclei plays an important role in exploring isospin mixing. The decay of at the proton drip line is studied using double-sided silicon strip detectors operating in conjunction with high-purity germanium detectors. The isobaric analog state (IAS) at 13 055 keV and two new high-lying states at 13 380 and 11 912 keV in are unambiguously identified through -delayed two-proton emission (). Angular correlations of two protons emitted from excited states populated by decay are measured, which suggests that the two protons are emitted mainly sequentially. We report the first observation of a strongly isospin-mixed doublet that deexcites mainly via two-proton decay. The isospin mixing matrix element between the IAS and the nearby 13 380-keV state is determined to be 130(21) keV, and this result represents the strongest mixing, highest excitation energy, and largest level spacing of a doublet ever observed in -decay experiments.
- Received 31 July 2022
- Revised 10 October 2022
- Accepted 3 November 2022
DOI:https://doi.org/10.1103/PhysRevLett.129.242502
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