First Accurate Normalization of the $\beta$-delayed $\alpha$ Decay of ${}^{16}$N and Implications for the ${}^{12}$C$(\alpha ,\gamma {)}^{16}$O Astrophysical Reaction Rate

Abstract

The ${}^{12}\text{C}(\alpha ,\gamma ){}^{16}\text{O}$ 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 $\alpha$ width, ${\gamma }_{11}$, of the bound $1^{-}$ level in ${}^{16}$O is particularly important to determine the cross section. The magnitude of ${\gamma }_{11}$ is determined via sub-Coulomb $\alpha$-transfer reactions or the $\beta$-delayed $\alpha$ decay of ${}^{16}$N, 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 [$b_{\beta ,11}=(5.02\pm 0.10)\times 10^{-2}$] and for $\beta$-delayed $\alpha$ emission [$b_{\beta \alpha }=(1.59\pm 0.06)\times 10^{-5}$]. 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 $\alpha$-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 ${}^{12}$C$(\alpha ,\gamma )$ cross section in the energy range relevant to hydrostatic He burning.

arXiv comment6 pages, 5 figures

References in corpus (5)

• The 12C(a,g)16O reaction and its implications for stellar helium burning
• Constraining the 6.05 MeV 0${}^{+}$ and 6.13 MeV 3${}^{-}$ cascade transitions in the ${}^{12}$C($\alpha$,$\gamma$)${}^{16}$O reaction using the Asymptotic Normalization Coefficients
• A Further Measurement of the beta-Delayed alpha-Particle Emission of 16N
• Measurement of the branching ratio for beta-delayed alpha decay of 16N
• A high efficiency, low background detector for measuring pair-decay branches in nuclear decay

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• Cluster effective field theory and nuclear reactions
• Impact of ${}^{16}$O($e,e^{\prime }\alpha$)${}^{12}$C measurements on the ${}^{12}$C($\alpha ,\gamma$)${}^{16}$O astrophysical reaction rate