Alpha and Cluster Decay in r-Process Nucleosynthesis

N.G. Kelkara, D.F. Rojas-Gamboaa, O.L. Caballerob, J.E. Perez Velasquezc aDepartamento de Fisica, Universidad de los Andes, Carrera 1E No. 18A-10, 111711, Bogotá, Colombia bDepartment of Physics, University of Guelph, N1G 2W1, Guelph, ON, Canada cFacultad del Medio Ambiente y Recursos Naturales, Universidad Distrital Francisco José de Caldas, Calle 13, No. 31-75, 111611, Bogotá, Colombia

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Elements from iron to uranium are expected to have been produced in the r-process nucleosynthesis via rapid neutron capture at elevated temperatures of the order of Giga Kelvins (GK). The network of coupled differential equations used to determine the abundance of elements thus involves nuclear reaction rates at elevated temperatures. The path of the r-process nucleosynthesis is along highly unstable nuclei and hence nuclear decay rates play an important role too. However, standard codes available for such calculations make use of terrestrial half-lives for alpha decay. Within a statistical approach and using data on excited nuclei, we find that for temperatures between 1-2 GK, the alpha decay half-lives can decrease by a few orders of magnitude as compared to the terrestrial ones. Based on these results, an estimate for the variations of the abundance of elements due to temperature-dependent half-lives is provided for a high entropy wind scenario. A model for the radioactive decay of thermally excited heavy nuclei by emitting an alpha or a light cluster such as 14C, 20O, or 28Mg is also presented and applied to evaluate the less known light cluster decay rates.

DOI:10.12693/APhysPolA.142.324 topics: alpha decay, cluster decay, r-process nucleosynthesis