The ${}^{13}C(\ensuremath{\alpha},n)$ reaction and its role as a neutron source for the $s$ process

The $^{13} C (α, n)$ reaction and its role as a neutron source for the $s$ process

M. Heil, R. Detwiler, R. E. Azuma, A. Couture, J. Daly, J. Görres, F. Käppeler, R. Reifarth, P. Tischhauser, C. Ugalde, and M. Wiescher

Phys. Rev. C 78, 025803 – Published 12 August 2008

Abstract

The $^{13} C (α, n)^{16} O$ reaction constitutes the dominant neutron source for the main $s$ process, which operates at a thermal energy of $kT = 8$ keV. Since the cross section at stellar energies is very small, the reaction rate cannot be directly determined and has to be extrapolated from cross section results obtained at higher energies. To remove various discrepancies in the normalization of previous data sets and to subsequently improve the reliability of the extrapolation, we performed measurements of the $^{13} C (α, n)^{16} O$ reaction in the energy range $E_{c . m .} = 320 − 700$ keV. In addition, the double differential scattering cross section $^{13} C (α, α)^{13} C$ was measured in the energy range $E_{lab} = 2.6 − 6.2$ MeV for 28 angles. These data were used to constrain possible contributions from background resonances for a reliable extrapolation with the multichannel $R$ -matrix code SAMMY. As a result, the uncertainties were significantly reduced, and a reaction rate of $(4.6 \pm 1.0) \times 10^{- 14}$ ${cm}^{3}$ /moles at $kT = 8$ keV ( $T = 0.1 \times 10^{9}$ K) was determined.

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Received 17 April 2008

DOI:https://doi.org/10.1103/PhysRevC.78.025803

Authors & Affiliations

M. Heil^1,*, R. Detwiler^2,†, R. E. Azuma^2,3, A. Couture^2,‡, J. Daly^2,§, J. Görres², F. Käppeler¹, R. Reifarth^1,∥, P. Tischhauser^2,¶, C. Ugalde^2,**, and M. Wiescher²

¹Forschungszentrum Karlsruhe, Institut für Kernphysik, Postfach 3640, D-76021 Karlsruhe, Germany
²University of Notre Dame, Department of Physics, Notre Dame, Indiana 46556, USA
³University of Toronto, Toronto, Ontario, M55 1A7, Canada

^*Present address: GSI Darmstadt, Planckstr. 1, D-64291 Darmstadt, Germany; M.Heil@gsi.de
^†Present address: University of Florida, Department of Nuclear and Radiological Engineering, P.O. Box 118300, Gainesville, FL 32611-8300, USA.
^‡Present address: Los Alamos National Laboratory, Los Alamos, NM 87545, USA.
^§Present address: Center for Naval Analysis, 4825 Mark Center Dr., Alexandria, VA 22311-1850, USA.
^∥Present address: GSI Darmstadt, Planckstr. 1, D-64291 Darmstadt, Germany.
^¶Present address: Microsoft Corp., Redmond, WA 98052, USA.
^**Present address: Department of Physics, University of North Carolina, CB3255, Chapel Hill, NC 27599, USA.

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Vol. 78, Iss. 2 — August 2008

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Physical Review C

covering nuclear physics

The $^{13} C (α, n)$ reaction and its role as a neutron source for the $s$ process

M. Heil, R. Detwiler, R. E. Azuma, A. Couture, J. Daly, J. Görres, F. Käppeler, R. Reifarth, P. Tischhauser, C. Ugalde, and M. Wiescher

Phys. Rev. C 78, 025803 – Published 12 August 2008

Abstract

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Physical Review C

covering nuclear physics

The 13C(α,n) reaction and its role as a neutron source for the s process

M. Heil, R. Detwiler, R. E. Azuma, A. Couture, J. Daly, J. Görres, F. Käppeler, R. Reifarth, P. Tischhauser, C. Ugalde, and M. Wiescher

Phys. Rev. C 78, 025803 – Published 12 August 2008

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The $^{13} C (α, n)$ reaction and its role as a neutron source for the $s$ process