Scission configuration in the self-consistent calculations with neck constraint

Abstract

The calculations of the potential energy surface are essential in the theoretical description of the fission process. In the constrained self-consistent approach, the smooth evolution of nuclear shape is described from the ground state until a very elongated one with a narrow neck. In all microscopic calculations, the rupture of the neck at scission is associated with a substantial change of nuclear matter density distribution and rapid energy decrease. In this paper, we show that there is no discontinuity of the potential energy surface at scission when multi-constrained calculations are applied with the neck constraint. An early rupture of the neck at lower quadrupole and octupole moments is discussed as competitive with the conventional fission path. We discuss the neck properties in the scission configuration. We find that the neck radius in the asymmetric fission mode cannot decrease below 2 fm, and the nuclear matter density cannot decrease below the saturation density. In the compact fission mode, nuclear density may go down to half of the saturation density before the rupture of the neck.

Microscopic description of cluster decays based on the generator coordinate method

“…In principle, we could use the microscopic density functional theory also for the tunneling process. However, this would require a large model space as well as a proper treatment of the neck degree of freedom [24,31] (see also Ref. [32]).…”

Dynamical synthesis of 4He in the scission phase of nuclear fission

“…In microscopic approaches, both geometrical and dynamical definitions of the scission configuration have been considered. Geometrical definitions include the criterion of vanishing density between the fragments, and the expectation value of a neck operator that gives a measure of the number of particles in the neck [15]. In a dynamical approach, the scission configuration can be defined in terms of the ratio of the nuclear and Coulomb interaction energies in the neck region [16], as well as using a quantum localization method based on the partition of orbital wave functions into two sets belonging to the pre-fragments [17].…”