Fission data obtained by multi-nucleon transfer reactions

Fission fragment mass distributions (FFMDs) obtained in multi-nucleon transfer (MNT) channels are presented. Experiments were carried out at the JAEA tandem facility in Tokai. The ¹⁸O beam is bombarded to several actinide nuclides, instead of using lighter projectile. It is advantageous in a sense that that data for a wider set of nuclei are obtained in one experiment, including neutron-rich nuclei which cannot be accessed by the traditional particle capture reactions. As the total excitation energies of the exit channel E^*_tot after MNT reaction distributes widely, we can investigate the excitation energy dependence of the FFMDs. In the MNT reactions, it is not well established how the E^*_tot is shared in between ejectile and recoil nucleus. This would bring an uncertainly to identify the excitation energy of the recoiled nucleus. However, some information answering this question would be obtained by comparing the shape of FFMDs and their E^*_tot dependence with those for proton-induced fissions that give the same initial compound nuclide with a uniquely identified excitation energy. In the comparison, it is seen that E^*_tot is mostly given to the recoiled (fissioning nucleus) up to the energies of around E^*_tot = 35 MeV. To explain the shape of FFMD measured in this energy region, the concept of 'multi-chance fission' is required to introduce, where neutron emission prior to fission generates less excited nucleus with small number of neutrons, contributing the pronounced peak-to-valley (P/V) structure in mass-asymmetric fission. (author)