Role of (α,n) reactions under r-process conditions in neutrino-driven winds reexamined

Peter Mohr
Phys. Rev. C 94, 035801 – Published 7 September 2016

Abstract

Background: The astrophysical r-process occurs in an explosive astrophysical event under extremely neutron-rich conditions, leading to (n,γ)(γ,n) equilibrium along isotopic chains which peaks around neutron separation energies of a few MeV. Nuclei with larger Z are usually produced by β decay, but under certain conditions also α-induced reactions may become relevant for the production of nuclei with Z+2.

Purpose: The uncertainties of the reaction rates of these α-induced reactions are discussed within the statistical model. As an example, α-induced (α,n) and (α,xn) reaction cross sections for the neutron-rich Se86 nucleus are studied in detail.

Method: In a first step, the relevance of (α,n) and (α,xn) reactions is analyzed. Next the uncertainties are determined from a variation of the α-nucleus potential which is the all-dominant parameter for the astrophysical ZZ+2 reaction rate.

Results: It is found that the r-process flow towards nuclei with larger Z is essentially influenced only by the α-nucleus potential whereas the other ingredients of the statistical model play a very minor role. This finding is based on the fact that the flow towards larger Z depends on the sum over all (α,xn) cross sections, which is practically identical to the total α-induced reaction cross section.

Conclusions: α-nucleus potentials play an important role under certain r-process conditions because the flow towards larger Z depends sensitively on the total α-induced reaction cross section. The uncertainty of the reaction rate is about a factor of two to three at higher temperatures and exceeds one order of magnitude at very low temperatures.

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  • Received 15 April 2016

DOI:https://doi.org/10.1103/PhysRevC.94.035801

©2016 American Physical Society

Physics Subject Headings (PhySH)

Nuclear Physics

Authors & Affiliations

Peter Mohr*

  • Diakonie-Klinikum, D-74523 Schwäbisch Hall, Germany and Institute for Nuclear Research (ATOMKI), H-4001 Debrecen, Hungary

  • *widmaiermohr@t-online.de

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Issue

Vol. 94, Iss. 3 — September 2016

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