Fusion-fission mechanism for synthesis of superheavy elements
Y. Aritomo (JINR Dubna)
The search for new elements is a long-standing important subject in nuclear
physics. The existence of the Island of Stability in superheavy mass region has
been predicted around Z=114 and N=184 using the macroscopic-microscopic model.
Recently, the production of new superheavy elements has been reported by GSI
(Z=110,111 and 112), FLNR (Z=113,114,115,116 and 118) and RIKEN (Z=110,111,112
and 113). In the theoretical study in this field, the dynamical aspects of the fusion-
fission mechanism have been investigated as a time evolution of the nuclear shape
taking into account friction. We apply a new method for calculation of multi-
dimensional potential energy with the extended two-center shell model. We take
into account the time evolution of the diabatic potential to the adiabatic one. In
the entrance and the exist channels, the neck parameter is different. And so we
consider the time-evolution of the neck parameter during the fusion-fission process.
In cold fusion reaction with Pb or Bi target, it is recognized that the nuclear
structure effects are very important in fusion process. Recently, the fragment mass
distributions for fission after full momentum transfer were measured for the reaction
36S + 238 U at several bombarding energies around the Coulomb barrier by JAEA. At
the incident energy E
c.m = 170 MeV, which corresponds to the excitation energy of
compound nucleus E* = 55 MeV, the Pb fragments are still measured remarkably.
It is the evidence that the shell structure remains at such excitation energy. By
analyzing the data, we investigate the whole fusion-fission process, and reveal the
roles of shell correction energy in fusion process.