A Nonequilibrium Information Entropy Approach to Ternary Fission of Actinides

TL;DR

This paper develops a nonequilibrium statistical approach to model ternary fission in actinides, linking isotope yields to nuclear states at scission and providing insights into the fission process through cluster production and reaction kinetics.

Contribution

It introduces a generalized Gibbs distribution within the nonequilibrium statistical operator method to describe isotope yields in actinide fission, incorporating excited states and continuum correlations.

Findings

Yields of light clusters are well described by nonequilibrium thermodynamics.

A saddle-to-scission relaxation time of about 7000 fm/c is estimated.

Light charged particle emission probes the nonequilibrium evolution of fissioning nuclei.

Abstract

Ternary fission of actinides probes the state of the nucleus at scission. Light clusters are produced in space and time very close to the scission point. Within the nonequilibrium statistical operator method, a generalized Gibbs distribution is constructed from the information given by the observed yields of isotopes. Using this relevant statistical operator, yields are calculated taking excited states and continuum correlations into account, in accordance with the virial expansion of the equation of state. Clusters with mass number $A \le 10$ are well described using the nonequilibrium generalizations of temperature and chemical potentials. Improving the virial expansion, in-medium effects may become of importance in determining the contribution of weakly bound states and continuum correlations to the intrinsic partition function. Yields of larger clusters, which fail to reach this quasi-equilibrium form of the relevant distribution, are described by nucleation kinetics, and a saddle-to-scission relaxation time of about 7000 fm/c is inferred. Light charged particle emission, described by reaction kinetics and virial expansions, may therefore be regarded as a very important tool to probe the nonequilibrium time evolution of actinide nuclei during fission.