Empirical limitations of energy dissipation in 252Cf(sf)

Limitations for the energy dissipated in the spontaneous fission of 252Cf were studied on the basis of the experimental fragment kinetic energies, neutron and γ data and the calculated (static) potential energies of the fragments. Upper bounds for the dissipated energy are obtained by restricting the parameter space of the fissioning system to the domain which is compatible with the experimental post-scission data, and by computing the maximum energy available in this domain for dissipation. No assumptions were made about the fission dynamics or the dissipation mechanism. A numerical evaluation was performed for 19 pairs of fragments in 252Cf(sf), taking into account spheroidal fragment shapes with diffuse surface, nuclear interaction and Coulomb excitation effects. The energy available for internal excitation at scission is found to be small (< or = to 10 MeV). An analysis of the uncertainties entering into this result shows that high dissipation in 252Cf(sf) is incompatible with the existing experimental data unless peculiar fragment shapes are assumed. Upper bounds are also given for the fragment deformations. The hypothesis of scission, minimum potential energy at the influence of fragment effects, and the relevance of data from ternary fission are discussed