Destruction of ¹⁸F via ¹⁸F(p,α)¹⁵O burning through the E_c.m.=665 keV resonance

Knowledge of the astrophysical rate of the ¹⁸F(p,α)¹⁵O reaction is important for understanding the γ-ray emission expected from novae and heavy-element production in x-ray bursts. The rate of this reaction is dominated at temperatures above ∼0.4 GK by a resonance near 7.08 MeV excitation energy in ¹⁹Ne. The ¹⁸F(p,α)¹⁵O rate has been uncertain in part because of disagreements among previous measurements concerning the resonance strength and excitation energy of this state. To resolve these uncertainties, we have made simultaneous measurements of the ¹H(¹⁸F,p)¹⁸F and ¹H(¹⁸F,α)¹⁵O excitation functions using a radioactive ¹⁸F beam at the ORNL Holifield Radioactive Ion Beam Facility. A simultaneous fit of the data sets has been performed, and the best fit was obtained with a center-of-mass resonance energy of 664.7±1.6 keV (E_x=7076±2 keV), a total width of 39.0±1.6 keV, a proton branching ratio of Γ_p/Γ=0.39±0.02, and a resonance strength of ωγ=6.2±0.3 keV.