Publication: First Accurate Normalization of the β-delayed α Decay of N-16 and Implications for the C-12(α,γ)O-16 Astrophysical Reaction Rate
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2018-10-03
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Amer Physical Soc
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Abstract
The C-12(alpha,gamma)O-16 reaction plays a central role in astrophysics, but its cross section at energies relevant for astrophysical applications is only poorly constrained by laboratory data. The reduced a width, gamma(11), of the bound 1(-) level in O-16 is particularly important to determine the cross section. The magnitude of gamma(11) is determined via sub-Coulomb a-transfer reactions or the beta-delayed a decay of N-16, but the latter approach is presently hampered by the lack of sufficiently precise data on the beta-decay branching ratios. Here we report improved branching ratios for the bound 1(-) level [b(beta,11) = (5.02 +/- 0.10) x 10(-2)] and for beta-delayed alpha emission [b(beta alpha) = (1.59 +/- 0.06) x 10(-5)]. Our value for b(beta alpha) is 33% larger than previously held, leading to a substantial increase in gamma(11). Our revised value for gamma(11) is in good agreement with the value obtained in a-transfer studies and the weighted average of the two gives a robust and precise determination of gamma(11), which provides significantly improved constraints on the C-12(alpha,gamma) cross section in the energy range relevant to hydrostatic He burning.
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Artículo firmado por 44 autores. We are grateful to the ISOLDE technical staff for providing excellent running conditions during the experiment, and thank the anonymous reviewers for their valuable comments and suggestions to improve the quality of the Letter. This work has been supported by the European Research Council under the ERC starting Grant Long Beamtime Experiments in Nuclear Astrophysics, No. 307447, the Horizon 2020 Research and Innovation Programme under Grant Agreement No. 654002, the Spanish Ministry of Economy and Competitiveness through Projects No. FPA2015-64969-P, FPA2015-65035-P, and FPA2017-87568-P, the Romanian Institutul de Fizica Atomica Grant CERN/ISOLDE, the United Kingdom Science and Technology Facilities Council, the Fonds voor Wetenschappelijk Onderzoek-Vlaanderen (Belgium) and GOA/2010/010 (Bijzonder OnderzoeksFonds KU Leuven), the German Federal Ministry of Education and Research under Contract No. 05P15PKCIA (ISOLDE) and Verbundprojekt 05P2015. B. J. acknowledges support from The Royal Society of Arts and Sciences in Gothenburg and OSK from the Villum Foundation through Project No. 10117.