Calculation of the fission-fragment yields of the pre-actinide nuclei by the example of the Pbnat isotopes

The calculations of the fission-fragment yields (mass and charge spectra) carried out within the frameworks of the proposed statistical method for the pre-actinide nuclei by the example of Pbnat (20 isotopes) are presented. The role of neutron shells with N = 50 and N = 82 in realizing the single- and double-humped shape of the fission-fragment yields, respectively, for the neutron-deficit and neutron-excess Pb isotopes has been investigated. An explanation of the experimental results on the Pbnat fission was performed taking into account transformations to the ensemble of the long- and short-lived nuclear fragments.