Scientists have unlocked a long-standing mystery in nuclear physics – the exceptional stability of certain atoms – by employing a mathematical approach akin to a variable-resolution microscope. The breakthrough sheds light on why atoms with specific numbers of protons and neutrons exhibit unusual resilience, a phenomenon first observed decades ago.
Nearly 80 years ago, Maria Goeppert Mayer posited that atomic nuclei with certain numbers of protons and neutrons, such as 50 or 82, displayed heightened stability. Subsequent research confirmed the existence of other “magic numbers” within the most abundant elements in the universe. While Goeppert Mayer initially envisioned each particle within the nucleus as independent, occupying discrete energy levels, modern quantum theory suggests strong interactions between these particles.
Researchers, led by Jiangming Yao of Sun Yat-sen University, have now demonstrated how these interactions give rise to the observed magic numbers. Their findings, published in Physical Review Letters, establish a link between the complex interplay of protons and neutrons and the resulting stability of atomic nuclei.
According to Yao, the original shell model was based on experimental data and lacked a detailed explanation of the interactions between individual particles. His team’s calculations, grounded in fundamental principles, precisely describe how these particles cluster together and the energy required to separate them. Maria Goeppert Mayer shared the 1963 Nobel Prize in Physics with J. Hans D. Jensen and Eugene Wigner for their discoveries concerning nuclear shell structure, becoming the second woman to win a Nobel Prize in Physics after Marie Curie in 1903.
The study’s authors likened their approach to capturing images of the same phenomenon at varying resolutions. “We started with the high-resolution description and gradually blurred it at each step of the calculation to clarify the evolution of the structure formed by the particles,” they explained. As they progressed, they observed changes in the symmetry of the quantum states of the particles. Plotting a graph based on the equations of these states revealed patterns with different symmetries at different resolutions. Nuclear structures reached maximum stability when particles grouped into magic numbers.
Jean-Paul Ebran, of the French Atomic Energy and Alternative Energies Commission, illustrated the concept by stating, “The nature appears different depending on the resolution at which it is observed.” He added that the identified change in symmetry is linked to the effects described by Albert Einstein’s theory of special relativity, providing a more comprehensive understanding of how magic numbers integrate different facets of nuclear theory.
Yao’s team tested their theoretical work on a type of tin, often referred to as “doubly magic,” with nuclei containing 50 protons and 82 neutrons. They plan to extend their analysis to heavier, generally more unstable nuclei, with potential implications for understanding stellar explosions and fusion.