The degree to which the $(p,\gamma )$ and $(p,\alpha )$ reactions destroy ${}^{18}\mathrm{F}$ at temperatures $(1-4)\times {10}^8\mathrm{K}$ is important for understanding the synthesis of nuclei in nova explosions and for using the long-lived radionuclide ${}^{18}\mathrm{F}$, a target of γ-ray astronomy, as a diagnostic of nova mechanisms. The reactions are dominated by low-lying proton resonances near the ${}^{18}\mathrm{F}+p$ threshold $(E_x=6.411\mathrm{MeV}$ in ${}^{19}\mathrm{Ne})$. To gain further information about these resonances, we used a radioactive ${}^{18}\mathrm{F}$ beam from the Holifield Radioactive Ion Beam Facility to selectively populate corresponding mirror states in ${}^{19}\mathrm{F}$ via the inverse ${}^2\mathrm{H}({}^{18}\mathrm{F},p){}^{19}\mathrm{F}$ neutron transfer reaction. Neutron spectroscopic factors were measured for states in ${}^{19}\mathrm{F}$ in the excitation energy range $0–9\mathrm{MeV}$. Widths for corresponding proton resonances in ${}^{19}\mathrm{Ne}$ were calculated using a Woods-Saxon potential. The results imply significantly lower ${}^{18}\mathrm{F}$$(p,\gamma )$${}^{19}\mathrm{Ne}$ and ${}^{18}\mathrm{F}$$(p,\alpha )$${}^{15}\mathrm{O}$ reaction rates than reported previously, thereby increasing the prospect of observing the $511\mathrm{keV}$ annihilation radiation associated with the decay of ${}^{18}\mathrm{F}$ in the ashes ejected from novae.

• Received 24 May 2004

DOI:https://doi.org/10.1103/PhysRevC.71.032801