Seminar Details

Fusion reactions with radioactive ion beams

Zach Kohley, NSCL
Thursday, May 10, 11:00 AM - Research Discussion
NSCL Lecture Hall

The unique radioactive ion beams available at the Holifield Radioactive Ion Beam Facility at Oak Ridge National Laboratory were used to study fusion reactions near and below the Coulomb barrier. Two open questions regarding heavy-ion fusion were addressed: (1) What is the role of transfer coupling in heavy-ion fusion? A number of previous studies have shown large enhancements in the sub-barrier fusion cross sections in correlation with the presence of positive Q-value neutron transfer channels. The fusion excitation functions of 132Sn+58,64Ni were measured and compared with stable Sn+Ni measurements. While the number of positive Q-value neutron transfer channels varied widely between the different Sn+Ni systems, the reduced excitation functions were equivalent. This suggests a significant change in the influence of transfer couplings on the Sn+Ni fusion process. (2) How does quasi-fission or fusion hindrance change as a function of isospin? The presence of quasi-fission in near-barrier reactions can hinder fusion by orders of magnitude. Experiments examining quasi-fission as a function of the neutron-richness of the reaction system have presented conflicting results. Through measuring the evaporation residue cross section for different radioactive Sn+Ni systems the fusion hindrance was estimated. The results indicate that the fusion hindrance does not increase with increasing neutron-richness.