Observation of the Astrophysically Important 3+ State in N18e via Elastic Scattering of a Radioactive F17 Beam from H1

The 17F(p,γ)18Ne reaction is important in stellar explosions, but its rate has been uncertain because of an expected 3+ state in 18Ne that has never been conclusively observed. This state would provide a strong ℓ=0 resonance and, depending on its excitation energy, could dominate the stellar reaction rate. We have observed this missing 3+ state by measuring the 1H(17F,p)17F excitation function with a radioactive 17F beam at the ORNL Holifield Radioactive Ion Beam Facility. We find that the state lies at a center-of-mass energy of Er=599.8±1.5stat±2.0syskeV ( Ex=4523.7±2.9 keV) and has a width of Γ=18±2stat±1syskeV.