Magnetic flips inside nuclei identified as source of unexpected low-energy gamma rays

A collaborative experiment at the Facility for Rare Isotope Beams, involving Lawrence Livermore National Laboratory researchers, has pinpointed magnetic transitions inside the nucleus as the cause of the long-standing low-energy gamma-ray enhancement. The team observed the decay of a radioactive copper isotope, separating an electric-type transition from a magnetic-type one; only the latter generated the surplus of low-energy photons.

Lead author Eleanor Ronning and co-lead Andrea Richard say this provides the first consistent theoretical link to the observed effect. The findings, appearing in Nature, could refine nuclear models used in energy production, national-security stockpile assessments, and forensic analysis of nuclear events. Moreover, the results may improve simulations of stellar explosions and neutron-star mergers that forge heavy elements. Ongoing work will test whether the magnetic mechanism applies across a broader range of isotopes.