Inversion of the Odd-Even Effect in Cold Fission from the Time-Dependent Pairing Equations

Abstract

Abstract.A peculiar phenomenon was observed experimentally in cold fission: the odd partition yields are favored over the even ones for excitations energies of the fragments smaller than 4 MeV. In this contribution, a microscopic model is proposed for the explanation of this odd-even effect in cold fission. This explanation is based on a mixing configuration mechanism that is produced during the fission process. This configuration mixing mechanism is obtained dynamically by solving a the generalized system of time-dependent pairing equations, which include a pair-breaking effect. The time dependent equations of motion for the pair breaking effect were corroborated with a condition that fixes dynamically the number of particles on the two fission fragment. The single particle level scheme was calculated with the Woods-Saxon superasymmetric two center shell model, providing a continuous variation of the single particle energies and of the wave functions from one nucleus up to two separated fragments. A first rule can be extracted from this model. The even-even fission products cannot be obtained at zero excitation energies because of the existence of dynamical excitations produced in the avoided-level-crossing regions when the nuclear system deforms slowly.

Influence of Prompt Neutron Emission on the Final Distribution of Mass, Kinetic Energy, and Charge of Fragments from Actinide Fission

“…In 2013, Gönnenwein confirms the negative odd-even effect [28]. In 2016, Mirea proposes a microscopic model to explain the negative odd-even effects on excitation energy in cold fission [29]. In 2017, Montoya and Collin show that there is no contradiction between the positive odd-even effect on TKE max and negative odd-even effect on TXE min as a function of Z [30].…”