One-Proton Breakup of $^{18}$F and the $^{17}$O(p,$\gamma )^{18}$F Reaction in Classical Novae

Classical nova studies are of considerable interest for understanding the chemical evolution of the Galaxy. They have been proposed as the most significant source for the nucleosynthesis of the isotopes $^{13}$C, $^{15}$N, and $^{17}$O in the Universe. Novae are also likely to synthesize the short-lived radioisotope $^{18}$F (T$_{1/2}=$ 110 min), which is expected to be the most important contributor to the observed emission of 511 keV gamma radiation by space-based $\gamma $-ray telescopes. This emission is produced by electron-positron annihilation following the beta$+$ decay of radioactive nuclei. A detection of these gamma rays could significantly constrain the nova simulation models. $^{18}$F nucleosynthesis in classical novae strongly depends on the thermonuclear rate of the $^{17}$O(p,$\gamma)^{18}$F reaction, which is part of the CNO cycle. This work presents preliminary results toward determination of the $^{17}$O(p,$\gamma )^{18}$F reaction cross section, which was measured by the indirect method of one-proton nuclear breakup at intermediate energies. The experiment was carried out at GANIL using a beam of $^{18}$F at 40 MeV/u impinging on a carbon target. Longitudinal momentum distributions of the $^{17}$O breakup fragments were measured in coincidence with $\gamma $-rays emitted by $^{17}$O residues.