Degrees of deformation at scission and correlated fission properties of atomic nuclei - art. no. 014612

The degrees of the deformation of atomic nuclei at scission configurations of the mass-symmetric and mass-asymmetric fission modes are studied. The be ta shape elongation of the fissioning nucleus, associated with the asymmetr ic fission is found to be constant for A(f)=213-260, while that associated with the symmetric fission is larger but also constant for a wide range of fissioning nuclei (A(f)=205-260) except for the low-energy induced and spon taneous fission of heavy nuclei with A(f)=245-262 when a change of the nucl eon number by one unit is found to cause a very rapid change in beta. A sys tematic correlation between the scission deformation and the fission proper ties such as the mass-yield distribution and the TKE are found. The constan cy of the beta gives rise to new formulas of TKEsym= 0.1173 x (Z(f)(2)/A(f) (1/3)) + 7.5 MeV for symmetric fission, and of TKEasym = 0.1217 x (Z(f)(2)/ A(f)(1/3)) + 3.5 MeV for asymmetric fission. The physical origin of the wel l-known simple Linear function for the TKE released in the fission process is found to be the invariance of the degrees of the elongation of scissioni ng nuclei. The mass dispersion of fission products was found to have a dire ct correlation with the beta value; as beta becomes larger, the width of th e mass yield distribution becomes wider. Our understanding of the spontaneo us fission properties of heavy nuclides in the Fm-258 region is presented. In this region, two different scission configurations, one giving beta simi lar to 1.53 which is the characteristic value for the asymmetric deformatio n and the other giving beta similar to 1.33 which is for the symmetric defo rmation, are found.