Deep inside a powerful accelerator in Caen, France, scientists have just captured something remarkable: a detailed map of mysterious high-energy light coming from more than a dozen heavy, unstable atomic nuclei — all in a single experiment. The breakthrough, published in the journal Physics Letters B, brings researchers closer to understanding one of nature's most complex phenomena: nuclear fission, the same process that powers some types of power plants. For the first time ever, physicists measured gamma-ray emissions from an entire family of exotic, neutron-rich nuclei that have never been studied with comparable methods. The two-week experiment combined two state-of-the-art instruments — the VAMOS++ magnetic spectrometer and the PARIS gamma-ray detector array — to catch and analyze radiation from these fleeting nuclei. When scientists fired uranium-238 ions at a beryllium-9 target, the collision created curium-247 nuclei that rapidly split apart into lighter fragments. VAMOS++ identified each fragment, while PARIS recorded the gamma rays it released. This allowed researchers from the Institute of Nuclear Physics in Krakow, Poland, along with international partners, to assign specific gamma-ray emissions to individual isotopes — something never achieved at this scale before. The measurements revealed clues about a phenomenon called "pygmy resonances." These occur in heavy nuclei containing many more neutrons than protons. The excess neutrons form a thin layer near the nuclear surface called a neutron skin. When struck, these neutrons vibrate collectively, emitting particularly energetic gamma rays. The team found evidence that at least some of the observed gamma rays come from these pygmy resonances. Dr. Michal Ciemala from the Krakow institute noted that observing the excited nuclei produced in curium fission was crucial, as it gave access to heavy nuclei that had never been investigated using comparable methods. The work studied nuclei near tin-132, a doubly magic isotope with completely filled proton and neutron shells. By mapping how these unstable nuclei behave, scientists can refine their models of fission — knowledge that ultimately helps improve reactor design and nuclear safety worldwide.