Inspenet, September 6, 2023.
Scientists discover new isotopes!
A team of scientists led by nuclear physicist Yosuke Kondo of the Tokyo Institute of Technology has discovered two isotopes of oxygen that have never been previously observed. These are oxygen-27 and oxygen-28 , which contain 19 and 20 neutrons, respectively.
The research was carried out at the RIKEN Nishina Center, a cyclotron accelerator facility designed to generate unstable isotopes.
To create these new isotopes, the team initially directed a beam of calcium-48 isotopes at a beryllium target. The collision spawned several lighter atoms, including fluorine-29, an isotope of fluorine with 9 protons and 20 neutrons. Fluorine-29 was then isolated and bombarded with a liquid hydrogen target. The goal was to remove a proton from fluorine-29, transforming it into oxygen-28.
Surprisingly, this isotope decayed rapidly, which goes against predictions based on magic number theory. Using advanced modeling techniques, the team of scientists has confirmed with 98% confidence that oxygen-28 does not have a coupled nucleus.
Both the number 8 and 20 are magic numbers for protons and neutrons, respectively, a feature that suggests that oxygen-28 should be stable. The total number of each depends on how the addition of each nucleon affects the stability of the proton and neutron shells.
In nuclear physics, a magic number refers to the number of nucleons that will completely fill a shell, with each new shell being clearly distinguishable from the last due to a wide difference in energy . An atomic nucleus that has shells of protons and neutrons that contain magic numbers of each is called “double magic” and is expected to be especially stable.
Most of the oxygen on Earth, including that found in the air we breathe, is oxygen-16, which is a form of oxygen considered doubly magical. It had long been anticipated that oxygen-28 would be the next doubly magical isotope after oxygen-16. However, new research challenges this idea.
This discovery raises questions about the reliability of the magic number concept. If an isotope with a magic number of protons and neutrons does not show the expected stability, does this mean that the theory itself is insufficient or requires revision? This questioning is at the center of current debates in nuclear physics, prompting scientists to re-examine and deepen their understanding of nuclear structure and the forces that govern it.
A deeper understanding of the strangely incomplete-seeming neutron shell will have to wait until scientists can investigate the nucleus in an excited state with higher energy levels.
Furthermore, other methods of oxygen-28 formation could shed light on this question, although their implementation is considerably more complex. For now, the intriguing and challenging results obtained by the team indicate that the nuclei considered doubly magical could be much more intricate than previously believed.
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