Charge distribution of heavy mass fission products in the thermal neutron induced fission of U, U and Pu.

Isobaric charge distribution has been carried out in the thermal neutron induced fission of U, U and Pu by measuring the fractional cumulative yields (FCY) of various heavy mass fission products within the range of 127-149. An off-line γ-ray spectrometric technique was used for the measurement of fission product activities. The width of the isobaric charge distribution (σ), most probable charge (Z) and thus the experimental charge polarization (ΔΖ) as a function of fragment mass were obtained. It was found that the σ values around the mass number 127-129 and 132-136 are lower due to the presence of spherical 50p and 82n shells. The ΔΖ values show an oscillating nature in the interval of five mass units due to even-odd effect. The ΔΖ values also show a decreasing trend with the approach of symmetric split besides an oscillating nature. The most probable charge (Z) and thus the ΔΖ values based on the minimum potential energy surface were theoretically calculated, which show a systematic decreasing trend with the approach of symmetric split due to the liquid drop behaviour of the fissioning nucleus.