Study of fission using multi-nucleon transfer reactions.

Multi-nucleon transfer channels of the reactions of ¹⁸O+²³²Th, ¹⁸O+²³⁸U, 18O+248Cm were used to measure fission-fragment mass distribution for various nuclides and their excitation energy dependence. Predominantly asymmetric fission is observed at low excitation energies for all the studied cases, with an increase of the symmetric fission towards high excitation energies. Experimental data are compared with predictions of the fluctuation-dissipation model, where effects of multi-chance fission (neutron evaporation prior to fission) was introduced. It was shown that a reliable understanding of the observed fission fragment mass distributions can be obtained only invoking multi-chance fissions. [ABSTRACT FROM AUTHOR]