Why not: Prompt Fission Neutrons are Released at Scission

The main properties of the neutrons released during the neck rupture and emitted immediately thereafter are calculated for 236U in the frame of a dynamical scission model. These properties are: the angular distribution with respect to the fission axis (calculated on spheres of radii R=30 and 40 fm and at time T = 4 × 10−21 sec), the distribution of the average energies of neutrons emitted from each state (calculated for durations of the neck rupture ΔT = 1 and 2 × 10−22 sec) and the total neutron multiplicity (calculated for two values of the minimum neck-radius rmin=1.6 and 1.9 fm). They are compared with measurements of prompt fission neutrons during 235U(nth, f). The experimental trends are well reproduced, i.e., the focussing of the neutrons along the fission axis, the preference of emission from the light fragment, the range, slope and average value of the neutron energy-spectrum and the average total neutron multiplicity. The neutron emission during a non-adiabatic scission process is therefore a viable alternative to the evaporation (from fully accelerated fragments) hypothesis.