Effect of nuclear structure and fissility on quasifission

In order to investigate the interplay between nuclear structure (shell closure) and dynamics, fission fragment mass distributions have been measured for reactions Cl-35,Cl-37 + Pb-206,Pb-208. These reactions have similar entrance channel parameters except for the number of closed shell configuration in the entrance channel. Fission fragment mass distributions have been measured for these reactions in the energy region close to the Coulomb barrier. No mass-angle correlation was observed in any of the four reactions, indicating the absence of fast quasifission (QF), but mass distributions were wider than that of compound nucleus (CN) fission, which indicates the presence of slow QF. With comparable fissility and deformation values, extra stability against QF was observed for reactions which have more closed shell configurations in the entrance channel. Mass-angle distributions of these reactions do not follow the systematics with respect to mean fissility. A new systematics has been obtained by considering quadrupole deformation of the heavy reaction partner along with the fissility, which explains the absence of mass-angle correlation in the presently measured reactions.