Lifetime of the astrophysically important 4.03-MeV state inNe19

Abstract

The $^{15}\mathrm{O}$($\ensuremath{\alpha},\ensuremath{\gamma}$)$^{19}\mathrm{Ne}$ reaction is one of the most important breakout reactions for the hot CNO cycles. However, the relevant states in $^{19}\mathrm{Ne}$ 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 \ensuremath{\gamma}- and \ensuremath{\alpha}-decay widths of the 4.03-MeV state of $^{19}\mathrm{Ne}$ 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 $^{17}\mathrm{O}$($^{3}\mathrm{He}$, $n\text{\ensuremath{-}}\ensuremath{\gamma}$)$^{19}\mathrm{Ne}$. For the 4.03-MeV state, the measured excitation energy is $4034.5\ifmmode\pm\else\textpm\fi{}0.8$ keV and the mean lifetime, measured here for the first time, is ${13}_{\ensuremath{-}6}^{+9}$ fs at the confidence level of $1\ensuremath{\sigma}$ and ${13}_{\ensuremath{-}9}^{+16}$ fs at the confidence level of $2\ensuremath{\sigma}$. This result is in excellent agreement with the 9-fs prediction by Langanke, Wiescher, Fowler, and G\"orres.