Imagine, for a moment, having the ability to peer into the heart of an atom. At its core resides the nucleus, housing tiny subatomic entities known as protons and neutrons. The element’s identity is determined by the number of protons it possesses; for instance, oxygen has eight protons. However, the count of neutrons within an atom can vary, giving rise to distinct versions of elements referred to as isotopes.
A recent breakthrough in scientific observation has introduced us to a previously unknown variety of oxygen—specifically, oxygen-28, characterized by having 20 neutrons. Researchers, operating within the Radioactive Isotope Beam Factory (please note, they aren’t producing miniature beams for packaging), have succeeded in producing oxygen-27 and oxygen-28 for the first time.
This achievement was accomplished by initiating a collision between an isotopic element, calcium-48, and a beryllium target. This collision yielded lighter atoms, ones with fewer protons and neutrons compared to the original element. Subsequently, scientists isolated fluorine-29 from these lighter atoms and subjected it to a collision with liquid hydrogen, causing the expulsion of the proton required to create oxygen-28.
However, the researchers were taken aback when oxygen-28 swiftly transformed into another isotope, challenging a fundamental assumption in nuclear physics concerning atomic stability.
Elements and their isotopes adhere to what scientists refer to as “magic numbers.” These are specific quantities of protons or neutrons within an atom that fill a certain nuclear shell, rendering the atom stable. If an atom possesses both a magic number of protons and a magic number of neutrons, it earns the designation of “doubly magic.” A well-known example of this phenomenon is oxygen-16, which is the most abundant oxygen isotope on Earth.
In this context, eight stands as a magic number for protons, and 20 for neutrons. Therefore, oxygen-28 was anticipated to be one such doubly magic isotope. However, its unexpected instability has prompted scientists to question whether 20 can truly be regarded as a magic number, potentially elucidating why it took so long to successfully detect oxygen-28.
Oxygen-28 isn’t the sole isotope where the presence of 20 neutrons no longer seems to confer magic status. In a phenomenon termed the “island of inversion,” isotopes of neon, sodium, and magnesium featuring 20 neutrons also display a lack of nuclear shell closure.
Regarding oxygen-28, the scientists involved in the study propose that further investigations will require examining the atom’s nucleus in a higher-energy state. This approach may offer a more comprehensive understanding of why 20 neutrons may not, in fact, be a magic number.
This groundbreaking study has been published in the journal Nature.
