The Average Lifetime of Giant Composite Systems Formed in Strongly Damped Collisions

The dynamic, adiabatic and diabatic entrance potentials in strongly damped reactions of U-238+U-238, Th-232+Cf-250 are calculated and compared. The feature of the dynamical potential implies that it is possible for the composite systems to stick together for a period of time. By means of the improved quantum molecular dynamics model the time evolution of the density and charge distributions of giant composite systems and their fragments for reactions U-238+U-238, Th-232+Cf-250 are investigated, from which the lifetimes of giant composite systems at different energies are obtained. The longest average lifetime of U-238+U-238, is found when the incident energy is about E-c.m.=1080MeV, which is about 1200fm/c.