Measurement of relative isotopic yield distribution of even-even fission fragments from $^{235}$U($n_{th}$,$f$) following $\gamma$ ray spectroscopy

TL;DR

This study provides the first detailed measurement of the relative isotopic yields of even-even fission fragments from $^{235}$U(n_th,f) using gamma-ray spectroscopy, supported by theoretical isospin conservation and GEF model calculations.

Contribution

It introduces a comprehensive experimental approach for analyzing isotopic distributions of even-even fission fragments and compares results with novel isospin conservation theory and semi-empirical models.

Findings

First detailed isotopic distribution data for even-even fission fragments.

Good agreement between experimental data and isospin conservation calculations.

Fair agreement with GEF semi-empirical model results.

Abstract

A detailed investigation on the relative isotopic distributions has been carried out for the first time in case of even-even correlated fission fragments for the $^{235}$U($n_{th}$,$f$) fission reaction. High-statistics data were obtained in a prompt $\gamma$ ray spectroscopy measurement during the EXILL campaign at ILL, Grenoble, France. The extensive off-line analysis of the coincidence data have been carried out using four different coincidence methods. Combining the results from 2-dimensional $\gamma-\gamma$ and 3-dimensional $\gamma-\gamma-\gamma$ coincidence analysis, a comprehensive picture of the relative isotopic yield distributions of the even-even neutron-rich fission fragments has emerged. The experimentally observed results have been substantiated by the theoretical calculations based on a novel approach of isospin conservation, and a reasonable agreement has been obtained. The calculations following the semi-empirical GEF model have also been carried out. The results from the GEF model calculations are found to be in fair agreement with the experimental results.