Dynamical model calculation to reconcile the nuclear fission lifetime from different measurement techniques

Abstract

The prescission particle multiplicities suggest a lifetime of $\ensuremath{\approx}{10}^{\ensuremath{-}20}$ s for nuclear fission to occur which is in contrast to the fission lifetime $\ensuremath{\approx}{10}^{\ensuremath{-}18}$ s as predicted by an atomic probe. This long-standing ambiguity, arising due to the orders of magnitude differences among the fission lifetimes measured from the nuclear and atomic probes, has been addressed within a dynamical model which includes the contributions from the nuclear shell effects. We show that at lower excitation energies, these two probes decouple as the fissioning system survives for a long time without any particle evaporation. We also consider a wide range of reactions to study the impact of the excitation energy of the compound nucleus on the fission dynamics in general. Prescission neutron multiplicity is found to be an inappropriate probe to measure fission lifetime at low excitation energy. In addition, our model predicts the average fission lifetime of the superheavy nucleus $^{302}120$ to be more than ${10}^{\ensuremath{-}18}$ s, which is in reasonable agreement with recent experiments.