Microscopic Evidence for Scission Neutrons

We present the first fully unrestricted microscopic calculation showing evidence for the existence of scission neutrons (SNs). In this contribution, we will show the results for the fission of 236U∗, 240Pu∗, and 252Cf within the time-dependent superfluid local density approximation (TDSLDA). We found a universal SN signal at the neck rupture across all trajectories examined so far, with three distinct neutron "clouds" emitted: two along the fission axis in front of the fission fragments (FFs), and one perpendicular to the axis of fission. We show there is a significant SN component to the prompt fission neutron (PFN) emission of ∼ 5 − 15% and that such neutrons are emitted with considerably higher kinetic energies than other PFNs. This phenomenon can partially account for the underestimation of the prompt fission neutron spectra at higher energies in some current phenomenological models. Additionally, we discuss some features of the neck rupture, including it's characteristic timescale, the evolution of the "formation" point, and the relationship between the rupture and SNs, particularly in connection with historically proposed mechanisms for SN emission. We also investigated charge emission at fission, which can act as an upper limit on ternary fission. Future studies can be improved by the inclusion of bigger lattices, more trajectories, and the inclusion of fluctuations.