THE FISSION YIELDS OF THE STABLE AND LONG-LIVED ISOTOPES OF XENON, CESIUM, AND KRYPTON IN NEUTRON FISSION OF U233

Abstract

The fission yields of Xe¹³¹, Xe¹³², Xe¹³⁴, Xe¹³⁶, Cs¹³³, Cs¹³⁵, Cs¹³⁷, Kr⁸³, Kr⁸⁴, 10.27 year Kr⁸⁵, and Kr⁸⁶ in the neutron fission of U²³³ have been determined by mass spectrometer methods. The very pronounced fine structure in the mass yield curve in the mass range 131 to 137 found in U²³⁵ fission does not occur in the fission of U²³³. This disappearance of fine structure would not have been predicted by any of the mechanisms which have been suggested to explain the fine structure in U²³⁵ fission. The fission yield of the 10.27 year isomer of Kr⁸⁵ relative to the other krypton isotopes is considerably higher in U²³³ fission than in U²³⁵ fission, indicating some fine structure in this mass range which may be related to the closed shell of 50 neutrons.