Why is the “watermelon” nucleus rewriting atomic science?

Finnish physicists have uncovered a groundbreaking discovery in nuclear physics with the identification of 188-astatine, the heaviest known nucleus to undergo proton emission.

This unique nucleus, described as “watermelon-shaped” due to its strongly prolate deformation, challenges previous understanding of atomic structure and nuclear interactions.

The 188-astatine isotope contains 85 protons and 103 neutrons and was detected using the RITU recoil separator at the University of Jyväskylä. It’s produced by a fusion-evaporation reaction that involved bombarding a silver target with strontium ions, making the process highly intricate due to the nucleus’s extreme rarity and short lifetime.

What is unique about the 188-astatine nucleus?

Unlike typical spherical nuclei, the watermelon shape denotes a strongly elongated, prolate structure, suggesting novel nuclear forces at play. Researchers observed a shift in the binding energy of the valence proton, indicating interactions previously unobserved in heavy nuclei.

Did you know?
The 188-astatine nucleus is the heaviest ever observed to emit a proton in radioactive decay.

How was the watermelon-shaped nucleus discovered?

The team combined experimental data with theoretical models to interpret the nucleus’s shape and properties. This discovery was part of Henna Kokkonen’s doctoral thesis, building on earlier work that identified new types of atomic nuclei.

What implications does this discovery have for nuclear science?

The finding expands the known limits of atomic matter and offers vital clues into the forces that govern nuclear stability and decay. Understanding proton emission in such heavy nuclei may offer novel knowledge about the processes fueling atomic transformations.

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What challenges did researchers overcome to make this finding?

Studying such exotic nuclei is difficult due to their fleeting existence and the extremely low production rates. The precision of the detector setup and the sophistication of the theoretical modeling were crucial to successfully identifying and characterizing the watermelon nucleus.

This record-breaking discovery marks a new chapter in nuclear physics, promising to influence ongoing research into the nature and behavior of atomic nuclei.