Speaker
Description
In this talk we will discuss the use of multi-nucleon transfer (MNT) reactions to study fission properties of a series of exotic nuclei in the neutron-rich actinide region. Most of these nuclei cannot be accessed by the traditional method of complete-fusion reactions. The MNT transfer channels of the $^{18}$O+$^{232}$Th reaction were used to study fission of fourteen nuclei $^{231,232,233,234}$Th, $^{232,233,234,235,236}$Pa, and $^{234,235,236,237,238}$U [1]. 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 (FFMDs) are measured for each transfer channel. In particular, the FFMDs of $^{234}$Th and $^{234,235,236}$Pa were 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. By using the same method, the measurements with $^{238}$U [2], $^{237}$Np, $^{248}$Cm, and $^{249}$Cf targets were recently performed.
The obtained FFMDs are compared with a calculation based on the fluctuation-dissipation model [2,3], where effect of multi-chance fission (neutron evaporation prior to fission) was considered. It was found that multi-chance fission has significant role on the shape of FFMD, particularly at the high-excitation energies.
Reference
[1] R. Leguillon et al., Phys. Lett. B 761, 125 (2016)
[2] K.Hirose et al., Phys. Rev. Letters, 119, 222501 (2017)
[3] Y. Aritomo and S. Chiba, Phys. Rev. C 88, 044614 (2013)
