Exploring quasifission characteristics for S 34 + Th 232 forming Sg 266

Background: Fission fragments from heavy ion collisions with actinide nuclei show mass-asymmetric and mass-symmetric components. The relative probabilities of these two components vary rapidly with beam energy with respect to the capture barrier, indicating a strong dependence on the alignment of the deformed nucleus with the partner in the collisions. Purpose: To study the characteristics of the mass-asymmetric quasifission component by reproducing the experimental mass-angle distributions to investigate mass evolution and sticking times. Methods: Fission fragment mass-angle distributions were measured for the S34+Th232 reaction. Simulations to match the measurements were made by using a classical phenomenological approach. Mass ratio distributions and angular distributions of the mass-asymmetric quasifission component were simultaneously fit to constrain the free parameters used in the simulation. Results: The mass-asymmetric quasifission component - predominantly originating from tip (axial) collisions with the prolate deformed Th232 - is found to be peaked near A=200 at all energies and center-of-mass angles. A Monte Carlo model using the standard mass equilibration time constant of 5.2×10-21 s predicts more symmetric mass splits. Three different hypotheses assuming (i) a mass halt at A=200, (ii) a slower mass equilibration time, or (iii) a Fermi-type mass drift function reproduced the main experimental features. Conclusions: In tip collisions for the S34+Th232 reaction, mass-asymmetric fission with A∼200 is the dominant outcome. The average sticking time is found to be ∼7×10-21 s, independent of the scenario used for mass evolution.