Primary fission fragment mass yields across the chart of nuclides

TL;DR

This paper presents a comprehensive computational method to predict primary fission fragment mass yields for over 3,800 heavy nuclei, aiding understanding of nucleosynthesis processes like the r-process.

Contribution

The authors introduce a novel Brownian shape motion model on potential-energy surfaces to calculate fission yields across the entire chart of nuclides, including microscopic effects.

Findings

Generated a large database of fission yields for 3,800+ nuclides.

Compared calculated yields with experimental data showing good agreement.

Identified general trends in low-energy fission yields across the chart.

Abstract

We have calculated a complete set of primary fission fragment mass yields, $Y(A)$, for heavy nuclei across the chart of nuclides, including those of particular relevance to the rapid neutron capture process ($r$ process) of nucleosynthesis. We assume that the nuclear shape dynamics are strongly damped which allows for a description of the fission process via Brownian shape motion across nuclear potential-energy surfaces. The macroscopic energy of the potential was obtained with the Finite-Range Liquid-Drop Model (FRLDM), while the microscopic terms were extracted from the single-particle level spectra in the fissioning system by the Strutinsky procedure for the shell energies and the BCS treatment for the pairing energies. For each nucleus considered, the fission fragment mass yield, $Y(A)$, is obtained from 50,000 -- 500,000 random walks on the appropriate potential-energy surface. The full mass and charge yield, $Y(Z,A)$, is then calculated by invoking the Wahl systematics. With this method, we have calculated a comprehensive set of fission-fragment yields from over 3,800 nuclides bounded by $80\leq Z \leq 130$ and $A\leq330$; these yields are provided as an ASCII formatted database in the supplemental material. We compare our yields to known data and discuss general trends that emerge in low-energy fission yields across the chart of nuclides.