FISSION FRAGMENT MASS DISTRIBUTION AS A PROBE OF THE SHAPE-DEPENDENT CONGRUENCE ENERGY TERM IN THE MACROSCOPIC MODELS.

The time evolution of nuclei at high excitation energy and angular momentum is studied by means of three-dimensional Langevin calculations performed for two different parameterizations of the macroscopic potential: the Finite Range Liquid Drop Model (FRLDM) and the Lublin-Strasbourg Drop (LSD) prescription. Depending on the mass of the system, the topology of the potential energy surface (PES), in the deformation space, is observed to be different within these two approaches. When incorporated in the dynamical calculation, the FRLDM and LSD models are observed to give similar results in the heavy mass region, whereas the predictions can be strongly dependent on the PES for fission of medium-mass nuclei. The shape-dependent congruence energy is only slightly modulated on the top of the bulk LD part although it changes the PES and the barrier height. [ABSTRACT FROM AUTHOR]