Experimental fission study using multi-nucleon transfer reactions

¹ Advanced Science Research Center, Japan Atomic Energy Agency, 2-4 Shirakata, Tokai, Naka-gun, Ibaraki 319-1195, Japan
² TRIUMF, Vancouver, British Columbia V6T 2A3, Canada
³ Laboratory for Advanced Nuclear Energy, Tokyo Institute of Technology, 2-12-1, Ookayama, Meguro-ku, Tokyo 152-8550, Japan
⁴ Faculty of Science and Engineering, Kindai University, Higashi-Osaka 577-8502, Japan
⁵ Research Reactor Institute, Kyoto University, Kumatori-cho, Sennangun, Osaka 590-0494, Japan
⁶ Université de Bordeaux, 351 Cours de la Libération, 33405 Talence Cedex, France
⁷ Centre des Sciences Nucléaire et des Sciences de la Matière, Université Paris-Saclay, CNRS/IN2P3, 91406 Orsay, France
⁸ Department of Physics, University of York, Heslington, York, YO10 5DD, UK

^a e-mail: nishio.katsuhisa@jaea.go.jp

Published online: 13 September 2017

Abstract

It is shown that the multi-nucleon 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, multi-nucleon transfer channels of the reactions of ¹⁸O+²³²Th, ¹⁸O+²³⁸U and ¹⁸O+²⁴⁸Cm are used to study fission for various nuclei from many excited states. 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. 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. Role of multi-chance fission in fission fragment mass distributions is discussed, where it is shown that mass-asymmetric structure remaining at high excitation energies originates from low-excited nuclei by evaporation of neutrons.