Fission within dinuclear system approach

Abstract

The improved scission-point statistical model based on the dinuclear system approach is employed to describe spontaneous fission, electromagnetic-, neutron-, charged-particle- and heavy-ion-induced fission of even–even pre-actinides, actinides and superheavy nuclei and to analyze the correlations between various observables. The key element of the model is the calculation of potential energy surfaces. The evolution of fission observables with increasing excitation energy is shown to be related with the widening and migration of the minima in the potential energy surface. Conservation of asymmetric shapes of mass and charge distributions of the fission fragments at high enough excitation energies of fissioning nuclei Hg, Pb, Rn, Ra, Th, U, Cf, Fm and No is predicted. At some critical excitation energy, the saturation of the symmetric component of charge and mass yields is demonstrated. For fissioning [Formula: see text]Hg, [Formula: see text]Fm and [Formula: see text]No, transitions from two-peaked to single-peaked mass distributions are predicted. The origin of the transition between asymmetric and symmetric fission modes with variations of neutron number and excitation energy is explored. For [Formula: see text]Hg(i.f.), [Formula: see text]Hg(i.f.), [Formula: see text]Fm(i.f.), [Formula: see text]Fm([Formula: see text], [Formula: see text]) and [Formula: see text]Fm(s.f.), the unexpected difference (symmetric or asymmetric) between the shapes of charge and mass distributions is predicted for the first time. The dependence of the neutron excess ratio of fission fragments on the fragment charge number is studied. A method is suggested for experimental verification of the multi-chance fission assumption. A possible explanation of the anomaly in charge yield of Mo/Sn fragments in the fission reaction [Formula: see text]U([Formula: see text], [Formula: see text]) at low excitation energies found by [Formula: see text]–[Formula: see text] coincidence spectroscopy is presented.