Speaker
Katsuhisa Nishio
(JAEA)
Description
Earlier studies of spontaneous fission of heavy actinides found that the fission-fragment mass distribution suddenly changes from predominantly asymmetric to symmetric, when the mass number of the fissioning nucleus becomes larger than 257. However, understanding of fission in this heavy-element and neutron-rich region is marginal due to limitation of experimental data.
At the JAEA tandem facility we have measured fission-fragment mass distributions of mendelevium nucleus, $^{258}$Md (atomic number 101), populated by the $^{4}$He+$^{254}$Es reaction. We found that mass-asymmetric and symmetric fission modes coexist in $^{258}$Md, and they strongly compete with excitation energy. Theoretical results will be also discussed.
Author
Katsuhisa Nishio
(JAEA)