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Deformed nuclei are doubly magical. Scientists have found the missing mass of zirconium-80

Scientist of the National Superconducting Cyclotron Laboratory (NSCL) and the Facility for Rare Isotope Beams (FRIB) at Michigan State University have solved the mystery of the missing mass of zirconium-80, a puzzle they have come across themselves. The experiments carried out at the NSCL have shown that the core of Zirconium-80containing 40 protons and 40 neutrons is much lighter than it should be. The theorists at FRIB have now carried out calculations that provide answers to the question of what happens to the missing mass.

The relationship between theorists and experimental physicists is like a coordinated dance, says lead author of the paper published in Nature Physics, Alec Hamaker. Sometimes it is the theorists who lead the way and show something before experimental discovery, and sometimes it is the experimenters discover something that the theorists did not expect, adds Ryan Ringle.

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The latest development is just a taste of what scientists around the world can expect. Already now offers the NSCL, the leading location in the USA for research with rare Isotopes, enormous opportunities for scientists. But the FRIB, which is slated to open next year, will be absolutely unique. Scientists from around the world will be able to make isotopes that are not available anywhere else. Facilities like the FRIB not only expand our knowledge of the universe, but also enable us to improve cancer treatments, for example. Ringle explains that the FRIB will enable previously inaccessible research and that the facility will provide new discoveries for many decades to come.

But let's get back to our 80Zr. It was made at the NSCL, and the facility's capabilities allowed scientists to measure its mass with unprecedented accuracy. The mass of this element had been measured before, but never as accurately. And these precise measurements revealed a lot of interesting things. Because if we can determine the mass so precisely, we are actually measuring a mass that has been lost. Because the mass of an atomic nucleus is not equal to the sum of the masses of Protons and Neutrons. Some of the missing mass manifests as energy holding the core together, explains Ringle.

We all remember Einstein's famous equation E = mc ^ 2. That means nothing else than that Mass and Energy are equivalent, they are equivalent. However, this can only be observed under extreme conditions such as those found in the atomic nucleus. Because if there is more binding energy between protons and neutrons in the nucleus, if they are more tightly bound to one another, then more mass is missing. And that is exactly the case with the zirconium-80 core, because new experiments have shown that the forces between neutrons and protons are greater than expected. And if so, the theorists had to find an explanation for why this happened.

So they examined the existing theories about 80Zr. They say, among other things, that this core could be a double magical core.
Previous experiments suggested that the Zirconium 80 core resembles a rugby ball rather than a ball. According to the theorists, this shape could contribute to the double "magic" of the core. Theorists have suspected for more than 30 years that the zircon 80 core is a deformed magic double core. It took the experimenters some time to prove this. And now that they have evidence to support the theory, the theorists can take the next step, Hamaker says.

The scientists are longingly waiting for the start of FRIB and hope to learn more about unusual cores like this zirconium-80 through this facility.