Employing TALYS to deduce angular momentum rootmean-square values, Jrms, in fission fragments

A Al-Adili,A Solders,V Rakopoulos

doi:10.1051/epjconf/202023903019

Abstract

Fission fragments exhibit large angular momenta J, which constitutes a challenge for fission models to fully explain. Systematic measurements of isomeric yield ratios (IYR) are needed for basic nuclear reaction physics and nuclear applications, especially as a function of mass number and excitation energy. One goal is to improve the current understanding of the angular momentum generation and sharing in the fission process. To do so, one needs to improve the modeling of nuclear de-excitation. In this work, we have used the TALYS nuclear-reaction code to relax excited fission fragments and to extract root-mean-square (rms) values of initial spin distributions, after comparison with experimentally determined IYRs. The method was assessed by a comparative study on 252Cf(sf) and 235U(nth,f). The results show a consistent performance of TALYS, both in comparison to reported literature values and to other fission codes. A few discrepant Jrms values were also found. The discrepant literature values could need a second consideration as they could possibly be caused by outdated models. Our TALYS method will be refined to better comply with contemporary sophisticated models and to reexamine older deduced values in literature.

Highlights

The generation of angular momentum (J) is an open question in contemporary fission modeling, which upon further exploration may improve our understanding of nuclear fission [1]
In this work we present a method to calculate average quantities of angular momenta, by utilizing the TALYS reaction code and comparing to measured Isomeric yield ratio (IYR) values[2, 4, 5]
The average excitation energy was derived based on the total excitation energy obtained from the GEF code[7]

Summary

Introduction

The generation of angular momentum (J) is an open question in contemporary fission modeling, which upon further exploration may improve our understanding of nuclear fission [1]. Novel techniques enable precise measurements of IYRs and allows systematic mapping of J as a function of compound mass, A, and excitation energy Eexc[2, 3]. In this work we present a method to calculate average quantities of angular momenta, by utilizing the TALYS reaction code and comparing to measured IYR values[2, 4, 5]. Literature IYR data, on 252Cf(sf) and 235U(nth,f), were used to estimate the Fission Fragment (FF) spin[6] and verified to a fair amount of reported literature spin values and the GEF code[7].

Results

Conclusion