Anomalous increase in width of fission fragment mass distribution in 19F+232Th

Fission fragment mass distribution has been studied for the system 19F+232Th over an energy range of 105.4 MeV to 84.2 MeV in laboratory frame. For energies, above the Coulomb barrier, the variance of the mass distributions σm2 varies linearly with temperature of the fused system, signifying statistical fusion-fission reaction. However, as energy decreases through the Coulomb barrier, a rapid increase in σm2 is observed for the first time which may be a signal of onset of orientation dependent quasifission reaction