Experimental evidence of shell effects in slow quasifission

Abstract

Mass distributions of fission fragments arising from the slow quasifission (SQF) process, derived by comparing the measured data with theory for several reactions, show distinct features. Irrespective of fissioning systems, the peak corresponding to lighter fragments in the SQF mass distribution is found to be always at $A\approx 96$, whereas the peak position of the heavier fragments increases linearly with the mass of the dinuclear system. Further, the yield of quasifission events decreases with the increasing projectile energy. These observations within certain model dependence provide clear evidences of shell effect in slow quasifission, where the lighter fragments are possibly some closed-shell nuclei in the mass region $A\approx 96$ (possibly ${}^{96}\mathrm{Zr}$ or ${}^{94}\mathrm{Sr}$). Further, the results from a model independent approach involving multi-Gaussian fit to the high energy data points reaffirm the above conclusion.