Exploring the Origin of Heavy Elements: Nuclear Input for P-Process Nucleosynthesis

Nuclear astrophysics is the study of how elements are created in various stellar environments and how such environments evolve. For example, stellar burning is responsible for the production of elements up to iron, and neutron capture processes create most of the heavy elements. However, the origin of heavy, proton-rich nuclei above iron is one of the greatest puzzles of stellar nucleosynthesis. The most likely scenario for creating these isotopes is the p-process: a complex network of photodisintegration reactions and their inverse (proton-, alpha- and neutron-capture) that occur during the explosion of a supernova. A vast network of 20,000 nuclear reactions for the p-process relies on models to provide input of nuclear properties and reaction rates for all the nuclei involved in the network. The goal of this project is to identify the reactions that are key for the p-process and to measure them directly, so as to minimize the uncertainty for those rates and provide constraints for the model predictions.

This project will contribute to understanding of the stellar p-process by measuring cross sections for proton and alpha capture reactions of relevance for Pd-102, Cd-108, Cd-110, Te-120 and Te-122. Those reactions have not been measured before, and have been identified as key for the p-process by two independent sensitivity studies. Studies have shown that the variations of those rates within the current model uncertainties have a significant impact on the production of the p-nuclei. The project will utilize a newly purchased detector (HECTOR) to employ the γ-summing technique. The impact of the measured reaction rates on the final abundances of the p-nuclei will be verified using network calculations whose results will be compared with the solar abundances. Additionally, the measured cross sections will be compared with model predictions and will be used to identify the model inputs that best reproduce the data.