Experimental Investigation of the ^{19}Ne(p,γ)^{20}Na Reaction Rate and Implications for Breakout from the Hot CNO Cycle.
The ^{19}Ne(p,γ)^{20}Na reaction is the second step of a reaction chain which breaks out from the hot CNO cycle, following the ^{15}O(α,γ)^{19}Ne reaction at the onset of x-ray burst events. We investigate the spectrum of the lowest proton-unbound states in ^{20}Na in an effort to resolve contradictions in spin-parity assignments and extract reliable information about the thermal reaction rate. The proton-transfer reaction ^{19}Ne(d,n)^{20}Na is measured with a beam of the radioactive isotope ^{19}Ne at an energy around the Coulomb barrier and in inverse kinematics. We observe three proton resonances with the ^{19}Ne ground state, at 0.44, 0.66, and 0.82 MeV c.m. energies, which are assigned 3^{+}, 1^{+}, and (0^{+}), respectively. In addition, we identify two resonances with the first excited state in ^{19}Ne, one at 0.20 MeV and one, tentatively, at 0.54 MeV. These observations allow us for the first time to experimentally quantify the astrophysical reaction rate on an excited nuclear state. Our experiment shows an efficient path for thermal proton capture in ^{19}Ne(p,γ)^{20}Na, which proceeds through ground state and excited-state capture in almost equal parts and eliminates the possibility for this reaction to create a bottleneck in the breakout from the hot CNO cycle.
Physics Department, Florida State University, Tallahassee, Florida 32306, USA.
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Belarge
Physics Department, Florida State University, Tallahassee, Florida 32306, USA.
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Kuvin
Physics Department, Florida State University, Tallahassee, Florida 32306, USA.
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Baby
Physics Department, Florida State University, Tallahassee, Florida 32306, USA.
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Baker
Physics Department, Florida State University, Tallahassee, Florida 32306, USA.
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Wiedenhöver
Physics Department, Florida State University, Tallahassee, Florida 32306, USA.
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Höflich
Physics Department, Florida State University, Tallahassee, Florida 32306, USA.
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Volya
Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Lousiana 70803, USA.
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Blackmon
Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Lousiana 70803, USA.
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Deibel
Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Lousiana 70803, USA.
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Gardiner
Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Lousiana 70803, USA.
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Lai
Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Lousiana 70803, USA.
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Linhardt
Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Lousiana 70803, USA.
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Macon
Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Lousiana 70803, USA.
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Need
Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Lousiana 70803, USA.
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Rasco
Department of Physics, University of North Florida, Jacksonville, Florida 32224, USA.
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Quails
Department of Physics, University of North Florida, Jacksonville, Florida 32224, USA.
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Colbert
Department of Physics, University of North Florida, Jacksonville, Florida 32224, USA.
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Gay
National Centre for Nuclear Research, ul. Andrezja Sołtana 7, 05-400 Otwock, Poland.
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Keeley