New proton emitter <sup>188</sup>At implies an interaction unprecedented in heavy nuclei.
basic_science · Level V
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- Record sourced from PubMed, PMID 40442077.
- Also identified by DOI 10.1038/s41467-025-60259-6 and PMC identifier 12122845.
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Abstract
We report the discovery of a new atomic nucleus <sup>188</sup>At, which is the heaviest proton-emitting isotope known to date. The new activity was observed through the <sup>107</sup>Ag(<sup>84</sup>Sr, 3n)<sup>188</sup>At fusion-evaporation reaction using the focal-plane spectrometer of the gas-filled recoil separator in the Accelerator Laboratory of the University of Jyväskylä, Finland. To fully interpret the experimental data, we have expanded the non-adiabatic quasiparticle model to treat nuclei in the beyond-lead region. The description reproduced the measured decay rate and pointed towards emission from an extremely prolate-deformed state with a dominant s<sub>1/2</sub> proton component in the wave function. The Thomas-Ehrman shift can be enhanced in low angular momentum states, but such effects have not been observed in heavy nuclei. The single-proton separation energy of <sup>188</sup>At deviates from that extrapolated from the systematics, which can be interpreted as the first evidence of this effect in heavy nuclei.