Evidence for Different Fission Behavior of Hot Nuclei Formed in Central and Peripheral Collisions of ⁴⁰Ar+²⁰⁹Bi Reaction at 25 MeV/u

Correlated fission fragments from the reaction of 25 MeV/u ⁴⁰Ar+²⁰⁹Bi and their further correlation with a particles have been studied for peripheral and central collisions simultaneously. The excitation energy at scission deduced from postscission multiplicity is about 172.5 MeV. The fission timescale deduced from prescission multiplicity is about 4 x10^-21 s. Systematic analysis of the mass and energy distributions of fission fragments as a function of the initial temperature of hot fissioning nuclei reveals the existence of different fission behavior of hot nuclei formed in central and peripheral collisions. Experimental data demonstrate the change of fission behavior at T ～ 4MeV.