Post-Neutron Mass Yield Distribution in the Thermal Neutron Induced Fission of ²³²U

In the thermal neutron–induced fission of ²³²U, cumulative and independent yields of various fission products within the mass ranges of 72 to 107 and 123 to 158 have been measured using an off-line gamma-ray spectrometric technique. The fission yields were determined relative to the yield of a monitor product ⁹²Sr. Charge distribution correction was applied on the cumulative yields to obtain the post-neutron mass yield distribution. Mass yield distribution parameters such as full-width at tenth-maximum of light and heavy mass wings, average light mass number <A_L> and heavy mass number <A_H>, and average number of emitted neutrons <ν> were obtained. Data from the present and earlier work on the ²³²U(n_th,f) reaction were compared with similar data of the ²³⁵U(n_th,f) reaction. It was found that the mass chain yield distribution in the ²³²U(n_th,f) reaction is asymmetric with two major humps as in the case of the ²³⁵U(n_th,f) reaction. Besides this, in the ²³²U(n_th,f) reaction, the mass yield distribution shows a small third hump for the symmetric fission products. It was also found that the standard II asymmetric mode of fission is favorable in the ²³²U(n_th,f) reaction whereas the standard I asymmetric mode of fission is favorable in the ²³⁵U(n_th,f) reaction.