An application of shell model to low-energy induced fission

One of the most challenging problems in nuclear physics is to describe

nuclear fission microscopically starting from nucleonic degrees of freedom.

Such microscopic description is important particularly for low-energy

induced fission, in which the excitation energy of the compound nucleus

is relatively low so that an application of the statistical model may be

questionable. This includes fission in r-process nucleosynthesis as well

as barrier-top fission. Here we shall discuss our recent attempts with

a shell model, for which many-body configurations are constructed based on

a constrained density functional theory for shapes along a fission path.

We specifically present our calculations with the Skyrme functional for a

neutron induced fission of 235U at barrier-top energies. In this exploratory

study, the configuration space is restricted only to neutron seniority-zero

configurations with a relatively small energy cutoff. We find that the

calculated fission-to-capture branching ratio is quite insensitive to the

fission decay widths of the pre-scission configurations, as is assumed

in transition-state theory. However, the probability flux at the barrier

appears spread out over many configurations rather than a few transition-state

channel.

Modeling barrier-top fission dynamics in a discrete-basis formalism

G.F. Bertsch and K. Hagino,

Phys. Rev. C107 (2023) 044615