Fission of heavy and superheavy nuclei at low excitation energies

The talk presents the results of an investigation of the main characteristics (mass and energy distributions of fission fragments and multiplicity of neutrons) of the fission of the nuclei of 220Ra, 226Th, 256No, 270Sg, 286112 produced in reactions with ions of 18O, 22Ne and 48Ca at energies close to and essentially below the Coulomb barrier. The data obtained show that the form of the mass and energy distributions of the fission fragments of 226Th and 270Sg is accounted for by the multimodal nature of the fission. In addition, for 226Th, a new phenomenon was established: there is a significant difference between the numbers of prescission neutrons for symmetric and asymmetric fission modes. It was found that, for the low-energy fission of the nucleus of 286112, the mass distribution of the fragments is of a clear-cut asymmetric form, contrary to what is observed for the spontaneous fission of the nuclei with Z=100-104 and for the induced fission of 270Sg