  The degree to which the (p,gamma) and (p,alpha) reactions destroy 18F at
temperatures 1-4x10^8 K is important for understanding the synthesis of nuclei
in nova explosions and for using the long-lived radionuclide 18F, a target of
gamma-ray astronomy, as a diagnostic of nova mechanisms. The reactions are
dominated by low-lying proton resonances near the 18F+p threshold (E_x=6.411
MeV in 19Ne). To gain further information about these resonances, we have used
a radioactive 18F beam from the Holifield Radioactive Ion Beam Facility to
selectively populate corresponding mirror states in 19F via the inverse
d(18F,p)19F neutron transfer reaction. Neutron spectroscopic factors were
measured for states in 19F in the excitation energy range 0-9 MeV. Widths for
corresponding proton resonances in 19Ne were calculated using a Woods-Saxon
potential. The results imply significantly lower 18F(p,gamma)19Ne and
18F(p,alpha)15O reaction rates than reported previously, thereby increasing the
prospect of observing the 511-keV annihilation radiation associated with the
decay of 18F in the ashes ejected from novae.
