Measurement of Radiative Proton Capture on 18F and Implications for Oxygen-Neon Novae

The rate of the ¹⁸F(p,g)¹⁹Ne reaction affects the final abundance of the gamma
-ray observable radioisotope ¹⁸F, produced in novae. However, no successful measurement of this reaction exists and the rate used is

calculated from incomplete information on the contributing resonances. Of the two resonances thought to

play a significant role, one has a radiative width estimated from the assumed analogue state in the mirror

nucleus, ¹⁹F. The second does not have an analogue state assignment at all, resulting in an arbitrary

radiative width being assumed. Here, we report the first successful direct measurement of the

¹⁸F(p,g)¹⁹Ne reaction. The strength of the 665 keV resonance (Ex = 7.076 MeV) is found to be over

an order of magnitude weaker than currently assumed in nova models. Reaction rate calculations show

that this resonance therefore plays no significant role in the destruction of ¹⁸F at any astrophysical

energy