Fission fragments mass distributions of nuclei populated by the multinucleon transfer channels of the O + Th reaction

Lguillon, R.; Nishio, Katsuhisa   ; Hirose, Kentaro  ; Makii, Hiroyuki   ; Nishinaka, Ichiro*; Orlandi, R.  ; Tsukada, Kazuaki  ; Smallcombe, J.*; Chiba, Satoshi*; Aritomo, Yoshihiro*; Otsuki, Tsutomu*; Tatsuzawa, Ryotaro*; Takaki, Naoyuki*; Tamura, Nobuyuki*; Goto, Shinichi*; Tsekhanovich, I.*; Petrache, C. M.*; Andreyev, A. N.

It is shown that the multinucleon transfer reactions is a powerful tool to study fission of exotic neutron-rich actinide nuclei, which cannot be accessed by particle-capture or heavy-ion fusion reactions. In this work, multinucleon transfer channels of the O + Th reaction are used to study fission of fourteen nuclei Th, Pa, and U. Identification of fissioning nuclei and of their excitation energy is performed on an event-by-event basis, through the measurement of outgoing ejectile particle in coincidence with fission fragments. Fission fragment mass distributions are measured for each transfer channel, in selected bins of excitation energy. In particular, the mass distributions of Th and Pa are measured for the first time. Predominantly asymmetric fission is observed at low excitation energies for all studied cases, with a gradual increase of the symmetric mode towards higher excitation energy. The experimental distributions are found to be in general agreement with predictions of the fluctuation-dissipation model.