Correlated transitions in TKE and mass distributions of fission fragments described by 4-D Langevin equation

Abstract

We have decomposed to symmetric and asymmetric modes the mass-TKE fission fragment distributions calculated by 4-dimensional Langevin approach and observed how the dominant fission mode and symmetric mode change as functions of of the fissioning system in the actinides and trans-actinide region. As a result, we found that the symmetric mode makes a sudden transition from super-long to super short fission mode around 254Es. The dominant fission modes on the other hand, are persistently asymmetric except for 258Fm, 259Fm and 260Md when the dominant fission mode suddenly becomes symmetric although it returns to the asymmetric mode around 256No. These correlated “twin transitions” have been known empirically by Darleane Hoffman and her group back in 1989, but for the first time we have given a clear explanation in terms of a dynamical model of nuclear fission. More specifically, since we kept the shape model parameters unchanged over the entire mass region, we conclude that the correlated twin transition emerge naturally from the dynamics in 4-D potential energy surface.

Evaluation of fission product yields and associated covariance matrices

“…Our transition from phenomenology to models with solid physical basis as far as possible makes it much easier to effectively feed back the going progress in fission physics [30], Lowell [31] and Yayoi [32]. Note that the vertical axis stands for the decay power (MeV/s) multiplied by the cooling time (s) for concise display on the linear s. [ 12,47,48] into the future revision of the FPY data library. Systematical trends for the model parameters we obtained in the present work will be published in a forthcoming paper, which will enable us to extend the present method to wider range of fissioning systems.…”

Progress in nuclear astrophysics of east and southeast Asia

“…It is planned to systematically measure the fission barrier of the neutron-rich actinoids with the SAMURAI setup at RIKEN RIBF. Nuclear data groups at Japan Atomic Energy Agency and Tokyo Institute of Technology successfully describe the FFD and their kinematical properties for long-lived radioactive actinoids and SHEs in a unique method of solving 3D/4D Langevin equation [238,239].…”

The Time-Dependent Generator Coordinate Method in Nuclear Physics

“…Certain diabatic aspects of the nuclear dynamics are then difficult to grasp with the corresponding GHW manybody wave function. This is the case of the dissipation as well as the viscosity of the shape dynamics predicted with Langevin methods [74,75] or time-dependent Hartree-Fock-Bogoliubov calculations. Past and ongoing studies to improve the description of these effects include efforts to quantize the Langevin equation [76,77], to couple the Langevin dynamics with the GCM [78] or to couple TDHFB trajectories with TDGCM [79].…”