Nuclear fission dynamics and fission time measurement

Nuclear fission is a dynamical process that needs time to occur. Nuclear dissipation is well known to slow down the fission process and is responsible for reductions of the statistical fission widths for the particle evaporation. Understanding of superheavy elements (SHEs) has become one of the long-standing questions in nuclear physics. The search for SHE started in the late 1960s. Initially in the process of fission and evaporation during a transient time, the statistical fission width progressively increases up to a stationary value. During this time, the particle evaporation is strongly favored. The alpha decay and also the spontaneous fission becomes an essential factor which determines the stability of superheavy elements (SHEs). Since the alpha decay, spontaneous fission, ternary fission and cluster radioactivity are essential to determine the decay of the compound nucleus during fission process. The longer fission time results observed are obtained using LISE ++ provides us with the quite direct evidence for the formation of compound nucleus of all possible isotopes with Z from 102 to 125 in Ge (74) + W, U (238) + Ge and the Th (232) + He and Ni (58) + W at 6.6 MeV/nucleon reactions. The agreement between the experimental results and our simulated results of spontaneous fission half-lives is very satisfactory. From these results we can conclude that the very long fission times (half-lives) can only show up if the fission barriers of all the isotopes involved in spontaneous fission are high enough to allow small percentage of long fission time before fission