Threshold states in 19Ne and the CNO breakout reaction 15O(α,γ)19Ne

摘要

The 15O(α,γ)19Ne reaction is one of the most important breakout reactions for the hot CNO cycles. However, the relevant states in 19Ne 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/lower limits. In particular, the accurate knowledge of the - and - decay widths of the 4.03 MeV state of 19Ne is important, since the resonance strength of this level dominates the reaction rate for the astrophysically relevant temperatures T9 < 0.6. In this work, we employed an improved DSAM approach to obtain lifetime values of this and other states via 17O(3He,n –γ )19Ne. 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 fs at the confidence level of 1 and 13 fs at the confidence level of 2. This result is in excellent agreement with the 9 fs prediction by Langanke, Wiescher, Fowler, and Gorres.