- Date:
- August 21, 2026
- Source:
- Lawrence Livermore National Laboratory (LLNL)
- Summary:
- For decades, scientists have puzzled over why certain atomic nuclei unexpectedly produce large numbers of low-energy gamma rays. A new experiment traced the effect to magnetic changes inside the nucleus, where protons and neutrons effectively flip their tiny internal magnets. The discovery could sharpen models of everything from nuclear reactions on Earth to the creation of heavy elements in stars and neutron star mergers.
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A decades-old puzzle in nuclear physics has centered on a strange question: why do some atomic nuclei release more low-energy gamma rays than scientists expect?
A new study led by the Facility for Rare Isotope Beams (FRIB), with researchers from Lawrence Livermore National Laboratory (LLNL), may provide the answer. Published in Nature, the findings offer new insight into the structure of atomic nuclei and could have important implications for astrophysics, nuclear energy, national security, and nuclear forensics.
Gamma rays are a form of electromagnetic radiation, just like visible light and radio waves. They are released when excited atomic nuclei lose energy and move into lower, more stable states during radioactive decay.
A Longstanding Gamma Ray Mystery
For decades, scientists have noticed that some nuclei emit an unexpectedly large number of low-energy gamma rays. This effect, known as "low-energy enhancement," has been difficult to explain. It does not appear in every nucleus, and researchers have not been able to reliably predict where it will occur.
"This low-energy enhancement wasn't predicted by theory, so it was kind of a shock to the community when it was first observed," said Eleanor Ronning, lead author of the study and former FRIB graduate student. "It is difficult to predict where [low-energy enhancement] occurs -- we don't know which nuclei will exhibit it."
The new results provide strong evidence that magnetic transitions within the nucleus are responsible for the effect.
"This is a key step forward," said Andrea Richard, co-lead of the study, former postdoctoral researcher at LLNL and current assistant professor at Ohio University. "We now have a consistent explanation that connects experimental observations with theory."
Separating Electric and Magnetic Nuclear Decay
To investigate the mystery, the researchers measured gamma rays produced as a radioactive copper isotope decayed into zinc. FRIB's specialized instruments and capabilities allowed the team to separate two distinct decay states and examine them individually.
In one state, the decay involved an electric transition. As the copper transformed, protons inside the nucleus shifted their positions.
The second state involved a magnetic transition. In this case, the neutrons and protons in the nucleus essentially flipped their internal magnets.
Only the magnetic transition produced the low-energy enhancement in gamma rays. That result showed that the phenomenon is magnetic in nature.
Ronning and Richard jointly proposed the experiment. Along with Richard's work as a postdoctoral researcher, other LLNL scientists contributed their expertise and helped monitor the experiment continuously during the weeklong, 24/7 run.
Implications for Nuclear Science and Security
Although the study focused on just one nucleus, the researchers say the findings could improve nuclear models across a much wider range of elements and reactions.
"We can improve the knowledge of our stockpile performance and interpretation of past test program results using the improved theory based on these discoveries," said author and LLNL scientist Darren Bleuel. "In addition, we can improve nuclear forensics -- our ability to determine if a nuclear event has occurred and identify the most likely source."
The findings could also help scientists better model nuclear reactions in stars, supernovae and neutron star mergers -- including the reactions responsible for creating heavy elements -- while improving understanding of processes relevant to nuclear energy.
Story Source:
Materials provided by Lawrence Livermore National Laboratory (LLNL). Note: Content may be edited for style and length.
Journal Reference:
- E. K. Ronning, A. L. Richard, S. N. Liddick, A. Spyrou, R. Ringle, H. Arora, H. C. Berg, J. M. Berkman, D. L. Bleuel, K. Bosmpotinis, S. E. Campbell, X. Chen, B. P. Crider, R. J. Coleman, P. A. DeYoung, A. A. Doetsch, H. Erington, T. Gaballah, N. D. Gamage, E. C. Good, B. Greaves, A. C. Hartley, J. Huffman, C. M. Ireland, C. Izzo, R. Jain, A. C. Larsen, J. E. L. Larsson, R. S. Lubna, F. M. Maier, M. J. Mogannam, D. Mücher, M. R. Mumpower, G. Owens-Fryar, T. H. Ogunbeku, D. P. Scriven, M. K. Smith, C. S. Sumithrarachchi, A. Sweet, K. Taft, A. Tsantiri, S. Uthayakumaar, M. Wiedeking. Magnetic character of the low-energy enhancement in 70Zn. Nature, 2026; 655 (8124): 875 DOI: 10.1038/s41586-026-10758-3
Cite This Page:
Facts Only
* A study led by FRIB researchers and LLNL researchers explored low-energy gamma rays from atomic nuclei.
* The effect observed is known as "low-energy enhancement."
* The research traced the effect to magnetic changes inside the nucleus, where protons and neutrons flip their internal magnets.
* Gamma rays are released when excited atomic nuclei lose energy during radioactive decay.
* Researchers measured gamma rays from a radioactive copper isotope decaying into zinc.
* The decay involved two states: one with an electric transition and one with a magnetic transition.
* Only the magnetic transition produced the low-energy enhancement in gamma rays.
* This result indicated that the phenomenon is magnetic in nature.
* The study focused on a specific nucleus, 70Zn.
* Findings may improve nuclear models related to reactions, heavy element creation, and nuclear forensics.
Executive Summary
A new study involving researchers from the Facility for Rare Isotope Beams (FRIB) and Lawrence Livermore National Laboratory (LLNL) investigated why certain atomic nuclei emit an unexpectedly large number of low-energy gamma rays, a phenomenon known as "low-energy enhancement." The research found that magnetic transitions within the nucleus are responsible for this effect. To investigate this, researchers measured gamma rays produced during the decay of a radioactive copper isotope into zinc, separating electric and magnetic transition states. The study concluded that only the magnetic transition caused the low-energy enhancement, demonstrating that the phenomenon is magnetic in nature.
The findings have implications across several scientific fields, including astrophysics, nuclear energy, national security, and nuclear forensics. The research suggests improvements to models concerning nuclear reactions, the creation of heavy elements in stars and neutron star mergers, and stockpile performance interpretation. Furthermore, the results can enhance the ability to determine the source of nuclear events for forensic purposes.
Full Take
The investigation successfully isolated a mechanism—magnetic transition—as the source of an unexplained gamma-ray enhancement, moving the puzzle from an observational anomaly to a theoretically grounded physical process. This successful separation between electric and magnetic decay states is methodologically significant, providing a clear framework for interpreting nuclear processes that were previously obscured by the mystery of "low-energy enhancement." The implication that internal magnetic fluctuations drive observable radiation connects fundamental quantum mechanics directly to macroscopic astrophysical events, such as stellar nucleosynthesis.
The real weight of this work lies in extending its scope. While the experiment focused on one isotope, establishing a consistent link between nuclear magnetism and decay products provides a crucial anchor point for refining complex theories used in areas like astrophysics and energy modeling. The potential application to nuclear forensics suggests that understanding these internal magnetic dynamics offers new avenues for tracing events and validating models of past nuclear activities. The next logical step involves determining how this specific magnetic interaction scales across the vast range of elements and extreme conditions found in stellar evolution, which requires bridging the gap between laboratory observation and cosmic scale physics.
Bridge Questions: How does the observed magnetic transition mechanism relate to existing models of strong-force interactions within the nucleus? What further experimental work is needed to confirm that this effect scales consistently across different nuclear systems relevant to astrophysics? What are the specific constraints imposed by magnetic transitions on the rates predicted by standard nuclear decay theory?