For the first time, a rare variant of oxygen known as oxygen-28 has been synthesized by scientists. Unlike oxygen-16, which is the prevalent form of the element, this unusual isotope has 12 additional neutrons.
Experts initially believed this “heavy” form of oxygen would be extraordinarily stable due to its unprecedented neutron count.
Contrary to expectations, the isotope disintegrated almost immediately. This surprising outcome calls into question the current understanding of the strong nuclear force, which is thought to bind elementary particles like protons and neutrons in an atomic nucleus.
Rituparna Kanungo, a physicist at Saint Mary’s University in Canada who was not part of the study, emphasized that “It opens a very, very big fundamental question about nature’s strongest interaction, the nuclear strong force.”
The experimental isotope was formed at Japan’s Riken RI Beam Factory in Wako by a team led by the Tokyo Institute of Technology. They directed a fluorine-29 beam at a liquid hydrogen target, triggering the creation of the elusive oxygen-28 molecule, as detailed in a study published in the journal Nature.
According to the Standard Model, the prevailing framework for understanding particle physics, particles should exhibit stability when their nuclear shells are filled with specific “magic” numbers of protons and neutrons.
With 20 neutrons and eight protons, both considered to be magic numbers, oxygen-28 was anticipated to be “doubly magic” and thus highly stable. But this was far from the truth.
During the test, the short-lived isotope disappeared within a zeptosecond—a time unit so small it’s a trillionth of a billionth of a second. Its existence was only verified by the residuals it left upon breaking down: oxygen-24 and four neutrons.
Takashi Nakamura, a physicist involved in the study, expressed his astonishment: “I was surprised.
“Personally, I thought it was doubly magic. But this is what nature says.”
Though this study awaits verification through further experiments, the results cast doubt on the existing list of magic numbers and their role in molecular stability.
A separate instance in 2009 demonstrated that an oxygen-24 isotope behaved as if it were doubly magic, despite lacking the theoretically required number of protons and neutrons.
According to Michael Thoennessen, a professor of physics at Michigan State University and study co-author, this groundbreaking research might serve as a stepping stone for future studies aiming to unravel the mysterious forces that hold particles together within an atomic nucleus.
“We still do not fully know what binds neutrons and protons together to form nuclei,” he told Live Science via email. “Exploring these extremes test the foundations of the nuclear models.”
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