Scientists unlock secrets of mercury isotope fission with 5D model

An international research team led by Associate Professor Chikako Ishizuka at Science Tokyo has developed a novel five-dimensional Langevin model that successfully explains the complex fission behavior of medium-mass mercury isotopes, particularly mercury-180 and mercury-190. Unlike previous models based on heavy elements like uranium and plutonium, which failed to capture mercury’s unusual asymmetric fission patterns, this new approach accurately reproduces the experimentally observed double-humped mass distributions and total kinetic energies of fission fragments. The model tracks the nucleus’s shape evolution in real time and incorporates a soft boundary in deformation space, as well as the dynamic influence of nuclear shell effects at excitation energies up to 40–50 MeV—contradicting earlier beliefs that these effects vanish at such energies. The study, published in Physical Review C and recognized as an Editor’s Suggestion, highlights that nuclear shell structure continues to play a significant role in fission dynamics even in lighter nuclei below atomic number 82. The researchers also