Impact of the New 22Ne(a,n)25Mg Reaction Rate on the Galactic Chemical Evolution

The slow neutron-capture process or s process is responsible for producing about half of the chemical abundances heavier than iron in the solar system. One of the most important nuclear reactions that produce neutrons in stars undergoing the s-process is the 22Ne(a,n)25Mg reaction. Recent studies of this reaction from Texas A&M University indicate that this reaction rate could be lower by about a factor of three from previously reported for typical He-burning temperatures. This study takes the new 22Ne(a,n)25Mg reaction rate and applies it in the s-process nucleosynthesis simulations of various stars with different initial masses (12-25 M☉) and metallicities (1.0<10-4-0.02). The stellar models were generated using the MESA code (Modules for Experiments in Stellar Astrophysics). The complete nucleosynthesis is calculated using the NuGrid post-processing nucleosynthesis code MPPNP. Here we particularly focus on core-collapse supernovae. These stellar yields are used to study the effects of the new 22Ne(a,n)25Mg reaction rates on the galactic chemical evolution (GCE) of the weak s-process elements, using the NuGrid/JINA-CEE one zone GCE code OMEGA.

This work at Brookhaven National Laboratory was sponsored by the Office of Nuclear Physics, Office of Science of the U.S. Department of Energy under Contract No.DE-Ac02-98CH10886 with the Brookhaven Science Associates, LLC. This project was supported in part by the U.S. Department of Energy, Office of Science, Office of Workforce Development for Teachers and Scientists (WDTS) under the Science Undergraduate Laboratory Internships Program (SULI). This project was supported in part by the Brookhaven National Laboratory (BNL), Nuclear Science and Technology Department under the BNL Supplemental Undergraduate Research Program (SURP).