DISSIPATIVE DYNAMICS OF HEAVY-ION FUSION-FISSION REACTION

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We have studied various subjects concerning the heavy-ion fusion-fission reaction from the viewpoint of dissipative dynamics.(1) We have developed a computer code for solving a multi-dimensional Langevin equation. We have improved the interpolation routine to obtain a good performance especially on super computers. We can solve 3- and 4- dimensional Langevin equation without difficulties.(2) We have analyzed the experimental data on the angular momentum dependence of prescission time obtained from the coincidence measurements of gamma-ray and charged particles. We have reproduced the experimentally deduced prescission time, including its angular momentum dependence.(3) We have analyzed the phenomenon of fusion hindrance using the 2- and 3-dimensional Langevin equation. We have reproduced the experimental data for symmetric-like systems, and also calculated the systems with large mass asymmetry.(4) We have studied the dynamical process of the synthesis of superheavy elements by dissipative dynamical models. First, we used the 1-dimensional Smoluchowski equation. Then, for a more realistic estimation, we proposed to divide the process in two stages and used 2-dimensional Langevin equation and 2-dimensional Smoluchowski equation for respective stages. We have predicted that the maximum yield is obtained around E^<**>=25MeV.(5) We have analyzed the new data on the fission lifetime obtained with the crystal blocking method. We used the statistical model and the dissiative dynamical model.(6) We have studied the fission of excited nuclei using the microscopic nuclear friction coefficient calculated by Dr. Yamaji, RIKEN.