Measurement of Radiative Proton Capture onF18and Implications for Oxygen-Neon Novae

The rate of the $^{18}\mathrm{F}(p,\ensuremath{\gamma})^{19}\mathrm{Ne}$ reaction affects the final abundance of the $\ensuremath{\gamma}$-ray observable radioisotope $^{18}\mathrm{F}$, 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, $^{19}\mathrm{F}$. 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 $^{18}\mathrm{F}(p,\ensuremath{\gamma})^{19}\mathrm{Ne}$ reaction. The strength of the 665 keV resonance (${E}_{x}=7.076\text{ }\text{ }\mathrm{MeV}$) 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 $^{18}\mathrm{F}$ at any astrophysical energy.