Charge distribution for light mass fission products in the thermal neutron induced fission of 229Th, 241Pu, 245Cm and 252Cf(SF)

Fractional cumulative yields (FCY) of various fission products in the light mass region have been determined in the thermal neutron induced fission of Th-229, Pu-241 and Cm-245 as well as in the spontaneous fission of Cf-252 using the direct gamma spectrometric technique. These data and similar data from the literature were used to deduce the charge distribution parameters such as the width parameter (sigma(z)), the most probable charge (Z(P)) and the charge polarization (Delta Z = Z(P-UCD)) as a function of the fragment mass for these four fissioning systems. Results of the present work along with our earlier work for heavy mass chains show smaller value of sigma(z) for N-P = 50 (A = 84-90) and Z(P) = 50, N-P = 82 (A = 128-136) indicating an effect of shell closure proximity where as the oscillating nature of sigma(z) and Delta Z in the interval of five mass units indicates;a proton pairing effect. Besides the oscillating nature, the Delta Z values decrease systematically with the approach of symmetric split which is characteristic of low energy fission.