Cold fragmentation properties of 252Cf (SF)

The spontaneous fission of 252Cf was investigated experimentally in the cold fission region. The fission fragment mass- and nuclear charge distributions were determined as a function of mass in total kinetic energy (TKE) bins of 2 MeV width in the TKE-range from 1 to 15 MeV and parallel to the average Qmax-value. There is no odd-even effect in the mass yield, whereas proton and neutron odd-even effects δZ and δN show linear dependence on (Qmax-TKE), however with different slopes. The present results lead to the conclusion that δZ and δN cannot be interpreted as indicators of the intrinsic excitation energy at scission, and that the structure of five to six mass units observed in many fission parameters finds its explanation in the shape of the Q-value surface in fission as a function of mass and nuclear charge in even-even fissioning systems. (orig.)