Improved Direct Measurement of the 64.5 keV Resonance Strength in the 17O(p,α)14N Reaction at LUNA

The O-17(p,alpha)N-14 reaction plays a key role in various astrophysical scenarios, from asymptotic giant branch stars to classical novae. It affects the synthesis of rare isotopes such as O-17 and F-18, which can provide constraints on astrophysical models. A new direct determination of the E-R = 64.5 keV resonance strength performed at the Laboratory for Underground Nuclear Astrophysics (LUNA) accelerator has led to the most accurate value to date omega gamma = 10.0 +/- 1.4(stat) +/- 0.7(syst) neV, thanks to a significant background reduction underground and generally improved experimental conditions. The (bare) proton partial width of the corresponding state at E-x = 5672 keV in F-18 is Gamma(p) = 35 +/- 5(stat) +/- 3(syst) neV. This width is about a factor of 2 higher than previously estimated, thus leading to a factor of 2 increase in the O-17(p,alpha)N-14 reaction rate at astrophysical temperatures relevant to shell hydrogen burning in red giant and asymptotic giant branch stars. The new rate implies lower O-17/O-16 ratios, with important implications on the interpretation of astrophysical observables from these stars.