Nuclear popcorn: Heavy nucleus changes shapes at different energies
A new paper sheds light on the nature of atomic nuclei.
Everything in the universe, from the largest galaxies down to individual atoms, is governed by four fundamental forces, which together describe how particles interact with each other and make up the world as we know it. These include the electromagnetic force, gravity and the weak and strong nuclear forces.
After a recent study out of the U.S. Department of Energy’s (DOE) Argonne National Laboratory and the University of North Carolina at Chapel Hill, researchers are one step closer to understanding the strong nuclear force, one of the most mysterious of the forces.
Their work builds on foundational theories of atomic structures that originated with Argonne physicist and Nobel Prize winner Maria Goeppert Mayer in the early 1960s. She helped develop a mathematical model for the structure of nuclei. Her model explained why certain numbers of protons and neutrons in the nucleus of an atom cause it to be extremely stable — a phenomenon that had baffled scientists for some time.
The research team previously conducted similar experiments to study the strong nuclear force by examining how the structure of a nucleus can change when it is produced in an excited state through a nuclear reaction. These and other experiments done elsewhere led them to investigate nickel-64, which has 64 neutrons and protons. This nucleus is the heaviest stable nickel nucleus, with 28 protons and 36 neutrons. This nickel isotope has properties that allow its structure to change when it is excited to higher energy states.
For their experiment, the team used the Argonne Tandem Linac Accelerator System, a DOE Office of Science user facility, to accelerate a sample of Ni-64 nuclei toward a target of lead. The lead atoms were able to excite the Ni-64 nuclei through the electromagnetic forces resulting from the repulsion between the protons in lead and the protons in nickel.
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