Nuclear Astrophysics

• Two papers on the s-process.
• Aspen workshop May/June 2005
• Starting in fall 2005 our nuclear astrophysics s-process team of five, including nuclear experimentalist Rene Reifarth, radioactive chemists Jon Schwantes (update 01/20/06: Jon Schwantes has left LANL) and Francois Nortier, nuclear theorists Toshihiko Kawano, and for the astrophysics modeling and simulation myself, are funded through a basic science LANL grant (LDRD-ER) on "The s-process in the Sm-Eu-Gd region - a probe for stellar mixing". Here is the proposal abstract:

  Evidence for nucleosynthesis in stars is observable in stellar spectra and meteorites, and is fundamental to understand the origin of the elements. Conversely, the observed elemental and isotopic abundances put strict constraints on models of stellar structure and evolution. At this time, a great opportunity for research at LANL is resulting from the confluence of four factors: enhanced observational data from ground and space-based observatories, the greatly improved sensitivity of isotopic abundance measurements in meteoritic inclusions, the new capability developed at LANL to measure reaction data on radioactive nuclides, and the LANL computing power and models. The goal of this proposal is to develop a new quantitative level of understanding of the origin of the elements through advanced models of stellar nucleosynthesis, which can be tested by the new observational and isotopic data. Crucial to these tests will be neutron-induced reactions on unstable nuclides, for which almost no nuclear reaction data exist. These data will be measured, evaluated, and incorporated into stellar nucleosynthesis networks that are linked to multidimensional simulations of mixing by LANSCE, C-INC, T-16, and T-6 scientists. Both the theoretical and experimental capabilities at LANL are unique in the world for this exciting and challenging nuclear astrophysics program. The nucleosynthesis in the proposed Sm-Eu-Gd region is uniquely suited for the proposed approach, because it is possible to experimentally complete the necessary nuclear data set and at the same time a wide range of observational high-quality data are available.

  We will hopefully soon have a dedicated web page for this project.

• The first looked at the charged-particle reactions of the oxygen isotopes, and specifically at the uncertainty of oxygen isoptic ratio predictions, that are used to interprete the corundum pre-solar grains.
• The second looked in two papers at the uncertainty of the ¹⁴N(p,gamma)¹⁵O, triple-alpha and ¹²C(alpha,gamma)¹⁶O reactions, and how they effect the simulation of carbon production in low-mass giants.