What can we learn from fission times?

摘要

Fission times have been measured by the blocking technique in single crystal for uranium nuclei and for super-heavy elements with Z = 120. The fission times measured for uranium nuclei can be reproduced by statistical calculations following the Bohr and Wheeler approach only if a friction coefficient increasing with temperature is considered. In the super-heavy element domain, a discrimination between the fast quasi-fission process and the slow fusion-fission one has been achieved from reaction time measurements. A minimum cross-section sigma = 22 mb for formation of Z = 120 compound nuclei in U-238+Ni reactions at 6.62 MeV/A has been inferred.