Angular and spin distributions of primary fission fragments

It is demonstrated that the formation of the fissile nucleus prescission configuration with two fis- sion prefragments connected by a neck is possible only with the simultaneous appearance of high values of relative orbital moments of the abovementioned prefragments, independently of their form. It is found that conservation of the fissile nucleus spin when its values are low leads to the formation of high values of pre- fragment spins , that are oriented antiparallel to the moment and perpendicular to the fissile nucleus symmetry axis. It is shown that for two deformed fission prefragments, the pumping mechanism of high values of their relative moments and spins , is due to the combined influence of bending- and wriggling- vibra- tions, the latter predominating. It is found that the high values of spherical fission prefragments are not related to thermal excitations but is determined by the excitation of the initial high-spin double quasiparticle states, due to the nonadiabatic collective deformation motion of the fissile nucleus in the vicinity of its rupture point. © 2011 Allerton Press, Inc.