Isomer-Yield Rations and Primary Angular Momenta of I, Xe and Cs Isotopes Produced in Thermal-Neutron Fission of ²³³U, ²³⁵U and ²³⁹Pu

Abstract

The independent isomer-yields of 132 I(4 + , 8 - ), 134 I(4 + , 8 - ), 135 Xe(3/2 + , 11/2 - ) and 138 Cs(3 - , 6 - ) have been measured in the thermal-neutron induced fission of 233 U, 235 U and 239 Pu. From the isomer-yield ratios, the mean angular momenta of the primary fragements have been deduced on the basis of thc statistical analysis. Obtained results indicate that the primary angular momentum \({\langle}J{\rangle}\hbar\) is higher in odd- Z products than in even- Z ones, and increases up to a certain value at an approximate rate of \({-\varDelta}{\langle}J{\rangle}/\varDelta(\delta N){\sim}0.8\hbar\) with decreasing neutron displacements δ N , which is defined as the difference between the number of neutron N in the products and the most probable neutron number N p in the isotopic yield distribution.