New discovery in nuclear physics: Chinese scientists reveal new proton magic number
- Prabhat R Mishra
- Jul 15
- 3 min read
In a remarkable breakthrough, scientists from the Institute of Modern Physics (IMP) at the Chinese Academy of Sciences have made significant strides in understanding the intricate world of nuclear physics.
Their recent research has revealed that the proton number 14 in the short-lived nucleus silicon-22 is a new "magic number," shedding light on the stability of atomic nuclei and the fundamental forces that govern them.
What are magic numbers?
Magic numbers in nuclear physics refer to specific counts of protons or neutrons that lead to particularly stable nuclei. These numbers, such as 2, 8, 20, 28, 50, 82, and 126, have long been recognized for stable, long-lived isotopes.
However, the magic numbers for exotic, short-lived isotopes have remained largely elusive. By studying these rare cases, researchers hope to unlock the secrets of the nuclear "building code" under extreme conditions, enhancing our understanding of how elements formed in the universe and the behavior of the nuclear force.
A historic measurement achieved by Chinese scientists
The IMP team’s findings, published in Physical Review Letters on July 2, mark the first precise measurement of the mass of silicon-22, a nucleus characterized by its short lifespan and deficiency in neutrons. This achievement is particularly noteworthy given the challenges associated with generating and measuring silicon-22, which has low yields and a fleeting existence.
Historically, scientists had theorized that the proton number 14 should be a magic number in silicon-22, based on the observed magic characteristics of neutron number 14 in its mirror nucleus, oxygen-22. However, until now, this prediction had remained unverified due to the difficulties in studying such exotic nuclei.
Innovative techniques lead to new insights
Utilizing advanced Bρ-defined isochronous mass spectroscopy at the Cooling Storage Ring of the Heavy Ion Research Facility in Lanzhou, the researchers successfully measured the ground-state mass of silicon-22. Their efforts also led to a nearly sevenfold improvement in the mass precision of silicon-23, another isotope.
The results revealed that silicon-22 possesses a positive two-proton separation energy, indicating that it does not spontaneously lose two protons. This finding confirms its status as a proton drip-line nucleus without two-proton radioactivity, resolving a long-standing debate in the field of nuclear physics.
By calculating the proton pairing energy of silicon-22 and comparing it with the neutron pairing energy of oxygen-22, the team established the new proton magic number 14. This discovery is further supported by the Gamow shell model, which provides a theoretical framework for understanding these phenomena.
A deeper understanding of exotic nuclei
While silicon-22 exhibits double-magic properties akin to those of oxygen-22, the study also found that its proton spatial distribution is more spread out compared to the neutron distribution of oxygen-22, indicating a slight symmetry breaking. This nuanced understanding of exotic nuclear structures offers new insights into nucleon interactions and the existence of extremely exotic nuclei.
The research was made possible through the support of the National Key R&D Program of China, the Strategic Priority Research Program of the Chinese Academy of Sciences, and the Youth Innovation Promotion Association of CAS, among others. As scientists continue to explore the mysteries of nuclear physics, this groundbreaking work paves the way for future discoveries that could reshape our understanding of the universe.
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