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Type of Document Dissertation Author Lee, Hye Young Author's Email Address hylee@anl.gov URN etd-12212006-094656 Title The 18F(α,p)21Ne Reaction and Its Astrophysical Implications Degree Doctor of Philosophy Department Physics Advisory Committee
Advisor Name Title Michael Wiescher Committee Chair Anthony Hyder Committee Member Ani Aprahamian Committee Member Peter Garnavich Committee Member Keywords
- implantation
- Hauser-Feshbach model
- resonance reaction
- r-process
Date of Defense 2006-12-18 Availability restricted Abstract Recent observations of the abundance distribution of heavy elements in metal-poor old stars suggest an existence of more than one r-process site, proposing a different site for the synthesis of light r-process nuclei. One model is the r-process nucleosynthesis in the supernova shock traveling through the He-rich shell of the pre-supernova star. In this scenario,the 14N from preceding CNO burning is converted to 18F, via
the reaction 14N(α,γ)18F and subsequent β+-decay
forms 18O, which then produces neutrons via
18O(α,n) or 18O(α,γ)22Ne(α,n) reactions.
The statistical model predicted that the 18F(α,p)21Ne reaction can compete with the β+-decay at high helium density and temperatures. Since 21Ne(α,n) has a positive Q-value, it has been identified as a
stronger neutron source than 22Ne(α,n). Because no published data on the 18F(α,p)21Ne reaction are available, we have measured the total cross sections of the 18F(α,p)21Ne reaction in inverse kinematics and the time-reverse reaction, 21Ne(p,α)18F.
The results were compared with
Hauser-Feshbach statistical model calculations. The astrophysical implications
of the new experimental reaction rate are discussed.
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