The Production of Trans-Lead Isotopes in the Intermediate Neutron Capture Process

Harvey, George

Abstract

In the field of stellar nucleosynthesis, there were long believed to be two neutron capture processes responsible for heavy element production, the slow (s) and rapid (r) processes. However, recently a third process has been discovered that lies between the other two, dubbed the intermediate or i-process. So far, only the r-process has shown signs of trans-lead production, but the i-process could have the potential to do so as well. I investigate whether the i-process is able to produce trans-lead isotopes and whether these isotopes will remain after an extended period of time. I use a one-zone simulation, altering the temperature between runs, to see whether a post-AGB star with a large hydrogen intake is able to produce significant amounts of trans-lead isotopes. I also introduce the neutron-induced fission reactions for trans-lead isotopes to return some of the material to lighter, more stable isotopes. When the temperature gets higher, there is an increase in the production of trans-lead isotopes. With the introduction of the neutron-induced fission reactions, the unstable trans-lead isotopes at the upper end of the nuclide chart decay, creating pools of stability around thorium and uranium with significant production of these elements. The results of these runs are then compared to the star HE 0338-3945, which is an i-process enriched system with upper limits determined for both Th and U. The comparison showed that the production of Th would be exceeded for one of the temperatures and never for Uranium. It is possible for the i-process sites to produce trans-lead material under the right conditions, but more research into the area is required. A more developed method for the neutron-induced fission products could be made using a distribution curve of results. Further insight into other observable i-process sites could further develop our understanding of the i-process and trans-lead isotopes.

Citation

Harvey, G. (2024). The Production of Trans-Lead Isotopes in the Intermediate Neutron Capture Process. (Thesis). University of Hull. https://hull-repository.worktribe.com/output/5001524

• Thesis Type: Thesis
• Deposit Date: Jan 6, 2025
• Publicly Available Date: Jan 16, 2025
• Public URL: https://hull-repository.worktribe.com/output/5001524
• Award Date: Jul 31, 2024