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

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).