Comparison of the Characteristics of the Fusion-Fissionand Quasifission Products in Reactions with Heavy Ions

Overlap of quasifission and fusion-fission product mass distributions measured for the 48Ca + 154Sm reaction at near-barrier energies is analyzed. As the incident ion energy increases, the angular distribution of quasifission fragments becomes narrower and they are concentrated near the forward and backward angles. The observed decrease in the yield of quasifission products with increasing collision energy is caused by noncoincidence of the product emission and detector position directions (the latter direction lags behind the beam direction by more than 15°) rather than by a decrease in the number of quasifission events. Our evaluations show that the excitation functions of evaporation residues in the 54Cr + 248Cm reaction are several orders of magnitude larger than the excitation functions for the other reactions, 58Fe + 244Pu and 64Ni + 238U, used to synthesize a new superheavy element with Z = 120 (A = 302)