Oxygen is one of the essential atoms for life, but it has more faces than we imagine. If we look at its molecules, for example, we can see that the properties of molecular oxygen (O2) are different from those of ozone (O3). But the oxygen atoms themselves also hold secret properties, and now an isotope of this element baffles experts.
Oxygen 28. A team of researchers has observed for the first time a new isotope of oxygen, oxygen 28, the most massive observed so far. This would not be particularly relevant (isotope 27 of the element was also observed for the first time) if it were not for the fact that they observed that this isotope did not behave in the way that the models predicted: it is an unstable isotope of oxygen.
The nucleus of oxygen 28 consists of eight protons (which gives it its properties as an element) and 20 neutrons, for a total of 28 nucleons. In contrast, the isotope of oxygen that most frequently occurs in our environment is oxygen 16, whose nucleus is composed of eight protons and eight neutrons.
Oxygen 16 is one of the three stable isotopes of oxygen, that is, those whose particles do not disintegrate naturally with the loss of protons or neutrons from their interior. The other two stable isotopes of oxygen are oxygen 17 and 18.
Less stable. Until now, experts believed, based on the most widespread theories on nuclear stability, that oxygen 28 was a stable isotope. However, when “creating” atoms in a laboratory they found that they disintegrated.
Oxygen isotopes can decay and transform into other elements, nitrogen or carbon, for example if the nucleus loses one or two protons respectively. However, the decay of isotopes 27 and 28 is produced by the loss of neutrons as observed by the researchers, which implies that they became another isotope of oxygen (oxygen 24).
““Magic numbers.” The discovery therefore implies that physicists are going to have to review this theory that predicted the stability of oxygen 28. In atomic and nuclear physics, the existence of a series of “magic numbers” is considered. In the case of atomic nuclei, magic numbers are associated with stability.
Both 8 and 20 are magic numbers, which would make oxygen 28 a “double magic” number, the researchers explained. The other known magic numbers are 2, 28, 50, 82 and 126.
Isotope Beam Factory. The researchers created this new isotope at the facilities of the RIKEN Radioactive Isotope Beam Factory, a research center located in Japan. The factory facilities have a cyclotron-type accelerator, thanks to which it is possible to create unstable isotopes.
The researchers accelerated a beam of calcium 48 atoms against a beryllium target to create fluorine 29, an isotope that would then be launched against hydrogen in order to make it lose a proton and become oxygen 28. The details of this process and its results were recently published in an article in the journal Nature.
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Image | RIKEN Radioactive Isotope Beam Factory / fdecomite