Unexpected Shape of Lead-208 Nucleus of May Force Scientists to Reevaluate Atomic Nuclei Models

"An international research collaboration led by the University of Surrey's Nuclear Physics Group has overturned the long-standing belief that the atomic nucleus of lead-208 is perfectly spherical," reports Phys.org. They add that the discovery "challenges fundamental assumptions about nuclear structure and has far-reaching implications for our understanding of how the heaviest elements are formed in the universe..."[A] new study published in Physical Review Letters used a high-precision experimental probe to examine its shape and found that rather than being perfectly spherical, the nucleus of lead-208 is slightly elongated, resembling a rugby ball (prolate spheroid)... Using the state-of-the-art GRETINA gamma-ray spectrometer at Argonne National Laboratory in Illinois, U.S., scientists bombarded lead atoms with high-speed particle beams accelerated to 10% of the speed of light - equivalent to circling the Earth every second. The interactions created unique gamma-ray fingerprints of the properties of excited quantum states in lead-208 nuclei - in other words, the nuclei were energized - which, in turn, were used to determine its shape. Theoretical physicists, including those at the Surrey Nuclear Theory Group, are now re-examining the models used to describe atomic nuclei, as the experiments suggest that nuclear structure is far more complex than previously thought.

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