A curious thing happened when MIT researchers Adam Vernon and Ronald Garcia Ruiz, along an international team of scientists, recently performed an experiment in which a sensitive laser spectroscopy technique was used to measure how the nuclear electromagnetic properties of indium isotopes evolve when an extreme number of neutrons are added to the nucleus. These nuclei do not exist in nature, and once created, their lifetimes can be as short as a fraction of a second, so the team artificially created the nuclei using a particle accelerator at the CERN research facility in Switzerland. By using a combination of multiple lasers and an ion trap, the team isolated the isotopes of interest and performed precision measurements of atoms containing these exotic nuclei. In turn, it allowed the extraction of their nuclear properties.

Vernon, a postdoc in the Laboratory for Nuclear Science (LNS); Garcia Ruiz, an assistant professor of physics and LNS affiliate; and their colleagues achieved a surprising result. When measuring a nucleus with a certain “magic” number of neutrons—82—the magnetic field of the nucleus exhibited a drastic change, and the properties of these very complex nuclei appear to be governed by just one of the protons of the nucleus.

“The new observation at 82 total neutrons changes this picture of the nucleus. We had to come up with new nuclear theories to explain the result,” says Vernon.

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After the Higgs, the Large Hadron Collider was expected to find other theorised particles. It didn’t, but particle physicists are optimistic about a new era of experiment-led exploration.

An investigation into a neutron-rich isotope of indium using a cutting-edge nuclear physics technique has begun to unravel the mysteries of how single particles behave inside the nucleus.

We have known that a nucleus is comprised of protons, which give an element its atomic number, and neutrons since the early 1930s. But how an individual proton or neutron behaves inside the heart of an atom is still poorly understood. Now, an international collaboration including scientists from Canada, China, Finland, France, Germany, Poland, Sweden, Switzerland, the UK and US has taken a step closer to understanding these complex interactions.

Nuclear physics researchers often look at elements with so-called ‘magic numbers’ of protons or neutrons, which are exceptionally well bound and thus highly stable. However, to learn about nuclear structure, nuclides with one fewer proton are used, known as a single proton hole. By investigating the electronic transitions, researchers can study the atomic, hyperfine structure of individual particles due to the interactions between electrons and the nucleus. This gives clues as to the nucleus’ magnetic and electric characteristics, which can then give a complete picture of how all protons and neutrons are distributed and interact inside a nucleus.