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The 15 O(α, γ ) 19 Ne reaction is one of the most important breakout reactions for the hot CNO cycles. However, the relevant states in 19 Ne at excitation energies of 4-5 MeV have not been well studied. The lifetimes of these states are not known and are only constrained by experimental upper and lower limits. In particular, accurate knowledge of the γ -and α-decay widths of the 4.03-MeV state of 19 Ne is important, since the resonance strength of this level dominates the reaction rate for the astrophysically relevant temperatures T 9 < 0.6. In this work, we employed an improved Doppler-shifted attenuation method to obtain lifetime values of this and other states via 17 O( 3 He, n-γ ) 19 Ne. For the 4.03-MeV state, the measured excitation energy is 4034.5 ± 0.8 keV and the mean lifetime, measured here for the first time, is 13 +9 −6 fs at the confidence level of 1σ and 13 +16 −9 fs at the confidence level of 2σ . This result is in excellent agreement with the 9-fs prediction by Langanke, Wiescher, Fowler, and Görres.

The neutron long counter NERO was built at the National Superconducting Cyclotron Laboratory (NSCL), Michigan State University, for measuring β-delayed neutron-emission probabilities. The detector was designed to work * Corresponding author. Tel.: +1 517 9087428; fax: +1 517 3535967Email address: pereira@nscl.msu.edu (J. Pereira) 1 Present address: Navy Nuclear Power School, Goose Creek, South Carolina, USA 2 Present address: Los Alamos National Laboratory, MS E540, Los Alamos, New Mexico, USA Preprint submitted to ElsevierMay 28, 2018 in conjunction with a β-decay implantation station, so that β decays and β-delayed neutrons emitted from implanted nuclei can be measured simultaneously. The high efficiency of about 40%, for the range of energies of interest, along with the small background, are crucial for measuring β-delayed neutron emission branchings for neutron-rich r-process nuclei produced as low intensity fragmentation beams in in-flight separator facilities.

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