Light element ($Z=1,2$) production from spontaneous ternary fission of $^{252}$Cf

TL;DR

This paper investigates the production of light elements from spontaneous ternary fission of $^{252}$Cf using a nonequilibrium approach that accounts for unstable nuclei, excited states, and medium effects, providing insights into dense matter and cluster formation.

Contribution

It introduces a nonequilibrium model incorporating continuum correlations and medium modifications to better describe light element yields from fission, surpassing simple equilibrium models.

Findings

Simple equilibrium models fail to reproduce isotope distributions.

Medium effects and continuum correlations significantly influence light cluster yields.

The nonequilibrium approach offers a more accurate description of the fission process.

Abstract

The yields of light elements ($Z=1,2$) obtained from spontaneous ternary fission of $^{252}$Cf are treated within a nonequilibrium approach, and the contribution of unstable nuclei and excited bound states is taken into account. These light cluster yields may be used to probe dense matter, and to infer in-medium corrections. Continuum correlations are calculated from scattering phase shifts using the Beth-Uhlenbeck formula, and the effect of medium modification is estimated. The relevant distribution is reconstructed from the measured yields of isotopes. This describes the state of the nucleon system at scission and cluster formation, using only three Lagrange parameters which are the nonequilibrium counterparts of the temperature and chemical potentials, as defined in thermodynamic equilibrium. We concluded that a simple nuclear statistical equilibrium model neglecting continuum correlations and medium effects is not able to describe the measured distribution of H and He isotopes. Moreover, the freeze-out concept may serve as an important ingredient to the nonequilibrium approach using the relevant statistical operator concept.