Understanding Neutron-Rich Environments By Examining Low-Energy Fusion Of Neutron-Rich Light Nuclei

Professor Romualdo deSouza (hosted by Dickhoff/Sobotka), Department of Chemistry and Physics, Indiana University, Bloomington Center for Exploration of Energy and Matter, Indiana University, Bloomington
January 27, 2017 at 12:00 pm
241 Compton
Event Description 

Nucleosynthesis via the r-process is responsible for production of approximately half the heavy elements. This process requires a neutron-rich environment such as a supernova or the merging of two neutron stars. Yet, the behavior of neutron-rich nuclei existing in such an environment remains an open question. It has been proposed for example that the enhanced fusion of neutron-rich light nuclei is responsible for igniting X-ray superbursts in accreting neutron stars. An isotopic chain of neutron-rich light nuclei provides a unique opportunity to study the fusion of two nuclei. On qualitative grounds the addition of neutrons to a projectile nucleus modifies the nuclear surface providing an increased attraction between projectile and target nuclei which should aid the fusion process. Thus, systematic investigation of an isotopic chain can provide an interesting test of how the nuclear surface evolves with addition of neutrons. To exploit this opportunity we have developed an experimental technique to investigate the fusion of neutron-rich light nuclei with low-intensity beams. We have used this technique to measure the fusion cross-section for 19O + 12C at near barrier energies and compare it with that of 18O + 12C. A clear and significant enhancement is observed for the neutron-rich projectile nucleus. These measurements have recently been extended to even more neutron-rich systems by measuring the fusion of 39,47K + 28Si. The experimental results are compared with a state-of-the-art microscopic model and the influence of pairing on the model predictions will be discussed.