Physicists Unveil Astatine-188: The Heaviest Proton-Emitting Isotope

June 18, 2025
Physicists Unveil Astatine-188: The Heaviest Proton-Emitting Isotope

In a groundbreaking discovery, physicists at the University of Jyväskylä in Finland have identified Astatine-188 (188At), the heaviest known proton-emitting isotope to date. The announcement was made on June 17, 2025, following the observation of two decay events using the focal-plane spectrometer of the gas-filled recoil separator at the university's Accelerator Laboratory. This innovative research marks a significant advancement in nuclear physics, shedding light on the properties and behaviors of exotic nuclei.

Astatine-188 possesses a unique composition of 85 protons and 103 neutrons, positioning it as the lightest known isotope of Astatine, which is a rare element found in trace amounts in nature. The discovery was reported by a research team led by doctoral researcher Henna Kokkonen, who emphasized the challenges associated with studying such exotic nuclei due to their short lifetimes and limited production cross sections. "Proton emission is a rare form of radioactive decay, in which the nucleus emits a proton to take a step towards stability," Kokkonen explained.

According to Dr. Kalle Auranen, another researcher involved in the study, the nucleus was synthesized through a fusion-evaporation reaction by irradiating a natural silver target with a Strontium-84 (84Sr) ion beam. The experimental setup utilized the RITU recoil separator, which allowed researchers to identify the new isotope and its decay characteristics. Auranen noted, "The precise techniques needed to analyze these isotopes are critical, given their transient nature."

Theoretical models were expanded to interpret the experimental data, revealing that 188At exhibits a strongly prolate shape, likened to a 'watermelon.' This shape suggests a potential trend change in the binding energy of the valence proton, possibly indicative of an unprecedented interaction within heavy nuclei. Kokkonen remarked, "Isotope discoveries are rare worldwide, and participating in such historical research is both challenging and exhilarating."

The implications of this discovery extend beyond Astatine-188 itself. The study enhances the understanding of nuclear stability and decay processes, potentially influencing future research on other isotopes, including the yet-unknown Astatine-189 (189At), which may also exhibit proton-emitting characteristics. The findings were published in the journal *Nature Communications*, with the reference: Kokkonen, H., et al. (2025). New proton emitter 188At implies an interaction unprecedented in heavy nuclei. Nat Commun 16, 4985; doi: 10.1038/s41467-025-60259-6.

This breakthrough is significant not only for the field of nuclear physics but also for its potential applications in medicine and energy. According to Dr. Lisa Thompson, a nuclear medicine expert at Stanford University, "Understanding the characteristics of such isotopes can open new avenues for targeted therapies in oncology, where isotopes are used for precise radiation treatment of cancers."

In conclusion, the discovery of Astatine-188 represents a notable contribution to the scientific community’s knowledge of nuclear physics, paving the way for future investigations into the behavior of isotopes and their practical implications. As researchers continue to explore the frontiers of atomic structure, the quest for understanding the limits of matter remains a compelling pursuit.

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Astatine-188proton-emitting isotopenuclear physicsUniversity of JyväskyläHenna KokkonenKalle Auranenisotope discoveryradioactive decaynuclear stabilityion beam irradiationNature Communicationsexotic nucleibinding energyfusion-evaporation reactionRITU recoil separatormedical applicationsnuclear medicinetargeted cancer therapyatomic structuredecay characteristicsheavy nucleiStrontium-84experimental physicsnuclear researchdecay eventstheoretical modelsproton emissionscientific breakthroughatomic nucleusisotope studies

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