Direct observation of slow fission from the width of K x-ray line

Amlan Ray,Sarmishtha Bhattacharyya,S Paul,A K Sikdar,A De,Soumik Bhattacharya,A Chatterjee,D Pandit,U Köster

doi:10.1051/epjconf/201819304004

Amlan Ray, Sarmishtha Bhattacharyya + Show 7 more

Open Access

https://doi.org/10.1051/epjconf/201819304004

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Abstract

An atomic clock based on the measurement of the intrinsic width of K x-ray lines has been used to obtain evidence of long-lived fission of the highly excited plutonium nuclei produced in the fusion of 4He+238U at E(4He)Lab=60 MeV. The mean fission time of the long-lived fission could be obtained from the increase of the intrinsic width of plutonium K x-ray line using quantum energy-time uncertainty principle. The presence of long-lived fission (mean fission time >1×10-18 s) has been found and the fluorescence yield per fission event shows that most of the fission events are slow (~10-18 s).

Highlights

The timescale of the nuclear fission process of highly excited fissile nuclei is a basic characteristic of the underlying fission dynamics
The different measured fission timescales have been attributed to the sensitivity of the nuclear technique to short timescale and that of atomic technique to long timescale and it was argued that the long fission times could provide information about the viscosity [8] of the nuclear medium and might be used as a probe [4] for studying the long-lived superheavy nuclei
It was recently shown [9] that the observed long fission time for the majority of the fissioning events as obtained by the atomic techniques cannot be reconciled with the short fission time obtained by the nuclear techniques for any plausible fission time distribution

Summary

Introduction

The timescale of the nuclear fission process of highly excited fissile nuclei is a basic characteristic of the underlying fission dynamics. The different measured fission timescales have been attributed to the sensitivity of the nuclear technique to short timescale and that of atomic technique to long timescale and it was argued that the long fission times could provide information about the viscosity [8] of the nuclear medium and might be used as a probe [4] for studying the long-lived superheavy nuclei. Since in 4He+238U fusion reaction, predominantly plutonium is produced by fusion and the effect of electronic configuration mixing should be small, narrow plutonium K x-ray lines should be seen in coincidence with the fission fragments, if there is a significant contribution from the long fission time component. According to Langevin fluctuation-dissipation model, there could be a significant contribution from a long-lived fission component, if the viscosity parameter is large leading to observable plutonium K x-ray yield and we have studied this possibility experimentally

Experiment and Data Analysis

Statistical significance of the results

Findings

Conclusions