[Bubble] First Accurate Normalization of the β-delayed α Decay of 16N and Implications for the 12C(α,γ)16O Astrophysical Reaction Rate

[Jay Benesch]

https://arxiv.org/abs/1804.02040

First Accurate Normalization of the β-delayed α Decay of 16N and 
Implications for the 12C(α,γ)16O Astrophysical Reaction Rate
O. S. Kirsebom, O. Tengblad, R. Lica, M. Munch, K. Riisager, H. O. U. 
Fynbo, M. J. G. Borge, M. Madurga, I. Marroquin, A. N. Andreyev, T. A. 
Berry, E. R. Christensen, P. Díaz Fernández, D. T. Doherty, P. Van 
Duppen, L. M. Fraile, M. C. Gallardo, P. T. Greenlees, L. J. 
Harkness-Brennan, N. Hubbard, M. Huyse, J. H. Jensen, H. Johansson, B. 
Jonson, D. S. Judson, J. Konki, I. Lazarus, M. V. Lund, N. Marginean, R. 
Marginean, A. Perea, C. Mihai, A. Negret, R. D. Page, V. Pucknell, P. 
Rahkila, O. Sorlin, C. Sotty, J. A. Swartz, H. B. Sørensen, H. 
Törnqvist, V. Vedia, N. Warr, H. De Witte
(Submitted on 5 Apr 2018)

     The 12C(α,γ)16O 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 α width, γ11, of 
the bound 1− level in 16O is particularly important to determine the 
cross section. The magnitude of γ11 is determined via sub-Coulomb 
α-transfer reactions or the β-delayed α decay of 16N, but the latter 
approach is presently hampered by the lack of sufficiently precise data 
on the β-decay branching ratios. Here we report improved branching 
ratios for the bound 1− level and for β-delayed α emission. In the case 
of the β-delayed α branch, we find a 5σ deviation from the literature 
value. With our new branching ratios, the constraints imposed on γ11 by 
the βα-decay and α-transfer data are of similar precision and, for the 
first time, in good agreement. The weighted average of the two gives a 
robust and precise determination of γ11, which may permit the 12C(α,γ) 
cross section to be constrained within 10% in the energy range relevant 
to hydrostatic He burning.