Speaker
Description
For a long time, ternary particle emission in low-energy fission has suggested the presence of non-equilibrium dynamics within the neck at the time of scission. We report a microscopic framework that follows the time evolution of nucleon densities in the neck of the fissioning system during the transition from saddle to scission. The shape evolution is modeled using multi-dimensional Langevin dynamics on macroscopic--microscopic potentials, generated from two-centered shell-model calculations. The hot neck region is treated as a dilute nuclear medium, where proton and neutron densities are fixed by local chemical potentials and propagated dynamically. Exciton populations are formed within discretized neck cells, which evolve through a momentum-space coalescence mechanism. That drives cluster formation, followed by decay via pre-equilibrium emission. As a test case we have chosen the reaction 235U, for which the model quantitatively reproduces the measured ternary yields from neutron to carbon isotopes, providing a unified dynamical description for ternary particle production in fission.
