Predictive Ternary Reactions for Stellar Nucleosynthesis

Project Overview

A major source of uncertainty in modeling the stellar abundances of elements heavier than iron comes from the fusion rate of two helium-4 nuclei (α particles) with a neutron (n) to produce beryllium-9 (i.e., α(αn,γ)9Be). This ternary fusion reaction is the most effective mechanism to bypass the roadblock owing to the lack of binary α+n and α+α bound systems in neutron-rich supernovae explosions. Because it is impossible to replicate the extremely high densities needed for the simultaneous (ternary) collision of the two α particles with the neutron in a laboratory, the α(αn,γ)9Be reaction rate cannot be directly measured with experiments.

To bypass this issue and make accurate predictions for this reaction rate we developed a fully microscopic theory for ternary reactions based on validated, state-of-the-art nuclear interactions, by combining the ab initio no-core shell model with the resonating group method (NCSM/RGM) and the Faddeev approach for the description of ternary systems. We demonstrated the importance of intrinsically three-body components of the nuclear interaction and took the first steps towards computing the full three-body capture of two α-particles and a neutron by extending the current codes to handle such systems. This project has significantly increased Lawrence Livermore National Laboratory's (LLNL) capabilities in describing ternary processes and has placed our team within reaching distance of providing the most accurate prediction for this reaction rate, a crucial input for reaction network calculations.

Mission Impact

This project has laid solid foundation for a new, much needed tool to accurately predict astrophysical ternary reaction rates that were previously out of reach (both experimentally and theoretically). The groundbreaking ab initio capability to describe reactions involving light nuclei above the three-particle breakup continuum, such as those to be measured at Facility for Rare Isotope Beams (FRIB), has helped establish LLNL as a leader in meeting the theoretical needs for FRIB science and will enable LLNL to meet future national security challenges. Furthermore, this capability will lead to increased capabilities in nuclear data evaluations that are leveraged to maintain and enhance the safety, security, and effectiveness of the U.S. nuclear weapons stockpile, by allowing for the exact treatment of ternary processes that take place in high energy density environments.

Publications, Presentations, and Patents

Hlophe, Linda, Konstantinos Kravvaris, and Sofia Quaglioni 2023. "Quantifying uncertainties due to irreducible three-body forces in deuteron-nucleus reactions." Physical Review C 107 1, 014315 DOI: 10.1103/PhysRevC.107.014315 

Daniel Bazin et al. 2023. "Perspectives on Few-Body Cluster Structures in Exotic Nuclei" Few Body Systems 64 2, 25

Hebborn, Chloë, et al. 2023. "Optical potentials for the rare-isotope beam era" Journal of Physics G: Nuclear and Particle Physics 50 060501 DOI: 10.1088/1361-6471/acc348

Linda Hlophe, "Towards a predictive description of direct nuclear reactions"  (Presentation, Theoretical Justifications and Motivations for Early High-Profile FRIB Experiments, East Lansing, MI, May 15-26, 2023). 

Linda Hlophe, "Irreducible Three-Body Forces in Deuteron-Nucleus Reactions: Faddeev Method vs Ab Initio Theory" (Presentation, INPC 2022, Cape Town, South Africa, September 11-19, 2022). 

Linda Hlophe, "Towards A Predictive Theory for Few-Body Nuclear Reactions" (Presentation, FRIB-TA Topical Program on Few-Body Clusters in Exotic Nuclei at Michigan State University, East Lansing, MI, August 15-26, 2022).

Linda Hlophe, "Quantifying Uncertainties Due to Irreducible Three-Body Forces on Deuteron-Nucleus Reactions" (Presentation, Nuclear Structure Conference at Lawrence Berkely National Laboratory, Berkeley, CA, June 13-17, 2022). 

Linda Hlophe, "Faddeev Approach to Deuteron-Induced Nuclear Reactions with Ab Initio Potentials" (Presentation, APS April Meeting, Virtual, April 9-12, 2022). 

Linda Hlophe, "Towards A Predictive Theory for Few-Body Nuclear Reactions" (Presentation, FRIB-TA Topical Program on Few-Body Clusters in Exotic Nuclei at Michigan State University, East Lansing, MI, August 15-26, 2022).

Linda Hlophe, "Uncertainties Due to Irreducible Three-Body Forces on Deuteron-Nucleus Reactions" (Presentation, FRIB-TA Topical Program on Optical Potentials at Michigan State University, East Lansing, MI, March 21 to April 1, 2022).

Linda Hlophe,  "Faddeev Approach to Deuteron-Induced Nuclear Reactions with Ab Initio Potentials" (Presentation, APS DNP Meeting, Virtual, October 10-14, 2021).