Measurement of the reaction 18O(α,n)21Ne

A. Best, S. Falahat, J. Görres, M. Couder, R. deBoer, R. T. Güray, A. Kontos, K.-L. Kratz, P. J. LeBlanc, Q. Li, S. O'Brien, N. Özkan, K. Sonnabend, R. Talwar, E. Uberseder, and M. Wiescher
Phys. Rev. C 87, 045806 – Published 29 April 2013

Abstract

Background: The reaction 18O(α,n)21Ne is a part of the reaction chains leading to the production of 19F and 22Ne during He burning in low-mass and massive AGB stars, respectively. Additionally, it has been observed as a strong background source in the measurement of other (α,n) reactions.

Purpose: Previously low-energy 18O(α,n)21Ne cross section data have only been available in a non-peer-reviewed form. An improved measurement of this reaction has been done to both clarify its astrophysical influence as well as to provide background yield data for future (α,n) experiments.

Method: The 18O(α,n(0+1)) reaction has been measured with a moderating neutron detector. In addition the (α,n1γ) channel has been measured independently by observation of the characteristic 350.7 keV γ transition in 21Ne. The reaction cross section at energies above Eα=1100 keV was determined by a simultaneous R-matrix fit to both channels. The strengths of the two lowest-energy resonances at Eα=959 keV and Eα=1066 keV were analyzed separately using individual Breit-Wigner fits.

Results: The cross section of both reaction channels, 18O(α,n0)21Ne and 18O(α,n1γ)21Ne, was determined from the threshold energies at 851 keV and 1280 keV, respectively, to 2300 keV. A new reaction rate has been deduced for the temperature range of 0.1 GK to 10 GK. A previously reported resonance at Eα=888 keV is explained as background from the contaminant reaction 17O(α,n)20Ne.

Conclusions: In general, our reaction rate is slightly lower than the reaction rates in recent compilations. At temperatures below 0.2 GK the present rate is significantly lower because it could be shown that the lowest reported resonance is background from the reaction 17O(α,n)20Ne that has been wrongly assigned to 18O(α,n)21Ne.

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  • Received 2 October 2012

DOI:https://doi.org/10.1103/PhysRevC.87.045806

©2013 American Physical Society

Authors & Affiliations

A. Best1,*, S. Falahat1,2, J. Görres1, M. Couder1, R. deBoer1, R. T. Güray3, A. Kontos1,†, K.-L. Kratz2, P. J. LeBlanc1,‡, Q. Li1, S. O'Brien1,§, N. Özkan3, K. Sonnabend4, R. Talwar1, E. Uberseder1, and M. Wiescher1

  • 1Department of Physics, University of Notre Dame, Notre Dame, Indiana 46556, USA
  • 2Department for Biogeochemistry, Max-Planck-Institute for Chemistry, 55020 Mainz, Germany
  • 3Kocaeli University, Department of Physics, Umuttepe 41380, Kocaeli, Turkey
  • 4Institute for Applied Physics, Goethe-University Frankfurt, 60325 Frankfurt, Germany

  • *Present address: Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA; abest1@nd.edu
  • Present address: National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI 48824, USA.
  • Present address: CANBERRA Industries, Inc., Meriden, CT 06450.
  • §Present address: US Government, Washington DC 20009.

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Issue

Vol. 87, Iss. 4 — April 2013

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