Entrance channel dependence of quasifission in reactions forming Th220

Mass-angle correlations of binary fragments produced in O16+Pb204, S34+W186, and Ti48,50+Er166,170 reactions have been measured for a range of bombarding energies around their Coulomb barriers. At above-barrier energies, the width of the mass distributions for the fission-like fragments in the Ti50+Er170 reaction are found to be higher than those from the same compound system at similar excitation energies populated via the more mass asymmetric entrance channel reaction S34+W186, which in turn is higher than those for the O16+Pb204 system. The width of the mass distributions of the Ti+Er systems is found to increase with decreasing bombarding energies, in contrast with those of the O16+Pb204 and S34+W186 systems, which show a monotonic reduction in mass widths. This may be associated with the elongated contact configuration at sub-barrier energies.