Decay properties of 22Ne + α resonances and their impact on s-process nucleosynthesis

S. Ota; G. Christian; G. Lotay; W.N. Catford; E.A. Bennett; S. Dede; D.T. Doherty; S. Hallam; J. Hooker; C. Hunt; H. Jayatissa; A. Matta; M. Moukaddam; G.V. Rogachev; A. Saastamoinen; J.A. Tostevin; S. Upadhyayula; R. Wilkinson

Physics Letters B (Mar 2020)

Decay properties of 22Ne + α resonances and their impact on s-process nucleosynthesis

S. Ota,
G. Christian,
G. Lotay,
W.N. Catford,
E.A. Bennett,
S. Dede,
D.T. Doherty,
S. Hallam,
J. Hooker,
C. Hunt,
H. Jayatissa,
A. Matta,
M. Moukaddam,
G.V. Rogachev,
A. Saastamoinen,
J.A. Tostevin,
S. Upadhyayula,
R. Wilkinson

Affiliations

S. Ota: Cyclotron Institute, Texas A&M University, College Station, TX 77843, USA; Corresponding author at: Cyclotron Institute, Texas A&M University, College Station, TX 77843, USA.
G. Christian: Cyclotron Institute, Texas A&M University, College Station, TX 77843, USA; Department of Physics & Astronomy, Texas A&M University, College Station, TX 77843, USA; Nuclear Solutions Institute, Texas A&M University, College Station, TX 77843, USA; Corresponding author at: Department of Astronomy and Physics, Saint Mary's University, Halifax, NS B3H 3C3, Canada.
G. Lotay: Department of Physics, University of Surrey, Guildford GU2 7XH, UK
W.N. Catford: Department of Physics, University of Surrey, Guildford GU2 7XH, UK
E.A. Bennett: Cyclotron Institute, Texas A&M University, College Station, TX 77843, USA; Department of Physics & Astronomy, Texas A&M University, College Station, TX 77843, USA
S. Dede: Cyclotron Institute, Texas A&M University, College Station, TX 77843, USA; Department of Physics & Astronomy, Texas A&M University, College Station, TX 77843, USA
D.T. Doherty: Department of Physics, University of Surrey, Guildford GU2 7XH, UK
S. Hallam: Department of Physics, University of Surrey, Guildford GU2 7XH, UK
J. Hooker: Cyclotron Institute, Texas A&M University, College Station, TX 77843, USA; Department of Physics & Astronomy, Texas A&M University, College Station, TX 77843, USA
C. Hunt: Cyclotron Institute, Texas A&M University, College Station, TX 77843, USA; Department of Physics & Astronomy, Texas A&M University, College Station, TX 77843, USA
H. Jayatissa: Cyclotron Institute, Texas A&M University, College Station, TX 77843, USA; Department of Physics & Astronomy, Texas A&M University, College Station, TX 77843, USA
A. Matta: Department of Physics, University of Surrey, Guildford GU2 7XH, UK
M. Moukaddam: Department of Physics, University of Surrey, Guildford GU2 7XH, UK
G.V. Rogachev: Cyclotron Institute, Texas A&M University, College Station, TX 77843, USA; Department of Physics & Astronomy, Texas A&M University, College Station, TX 77843, USA; Nuclear Solutions Institute, Texas A&M University, College Station, TX 77843, USA
A. Saastamoinen: Cyclotron Institute, Texas A&M University, College Station, TX 77843, USA
J.A. Tostevin: Department of Physics, University of Surrey, Guildford GU2 7XH, UK
S. Upadhyayula: Cyclotron Institute, Texas A&M University, College Station, TX 77843, USA; Department of Physics & Astronomy, Texas A&M University, College Station, TX 77843, USA
R. Wilkinson: Department of Physics, University of Surrey, Guildford GU2 7XH, UK

Journal volume & issue: Vol. 802

Abstract

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The astrophysical s-process is one of the two main processes forming elements heavier than iron. A key outstanding uncertainty surrounding s-process nucleosynthesis is the neutron flux generated by the Ne22(α,n)25Mg reaction during the He-core and C-shell burning phases of massive stars. This reaction, as well as the competing Ne22(α,γ)26Mg reaction, is not well constrained in the important temperature regime from ∼0.2–0.4 GK, owing to uncertainties in the nuclear properties of resonances lying within the Gamow window. To address these uncertainties, we have performed a new measurement of the Ne22(Li6,d)26Mg reaction in inverse kinematics, detecting the outgoing deuterons and Mg25,26 recoils in coincidence. We have established a new n/γ decay branching ratio of 1.14(26) for the key Ex=11.32 MeV resonance in Mg26, which results in a new (α,n) strength for this resonance of 42(11)μeV when combined with the well-established (α,γ) strength of this resonance. We have also determined new upper limits on the α partial widths of neutron-unbound resonances at Ex=11.112, 11.163, 11.169, and 11.171 MeV. Monte-Carlo calculations of the stellar Ne22(α,n)25Mg and Ne22(α,γ)26Mg rates, which incorporate these results, indicate that both rates are substantially lower than previously thought in the temperature range from ∼0.2–0.4 GK.

Published in Physics Letters B

ISSN: 0370-2693 (Print); 1873-2445 (Online)
Publisher: Elsevier
Country of publisher: Netherlands
LCC subjects: Science: Physics
Website: http://www.journals.elsevier.com/physics-letters-b/

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