Dynamical scission model

A time-dependent microscopic approach to the scission process, i.e., the transition from two fragments connected by a thin neck (image) to two separated fragments (image), which takes place in a short time interval ΔT, is presented. We follow the evolution from image to image of all occupied neutron states by solving numerically the two-dimensional time-dependent Schrödinger equation with time-dependent potential. Calculations are performed for mass divisions from image to image (image being the light-fragment mass). The duration of the neck rupture ΔT is taken as parameter having values from image to image. The resulting scission-neutron multiplicities image and primary fragment excitation energies image are compared with those obtained in the frame of the sudden approximation (image). As expected, the sudden approximation is an upper limit. For image, which is a realistic value, the time-dependent results are image to image below this limit. For transition times longer than image the adiabatic limit is reached. The probability and current densities of the unbound neutrons at scission are also calculated. They provide a detailed picture of the emission mechanism and a hint for the angular distribution of the scission neutrons with respect to the fission axis.