Simultaneous measurement of the 18F(p,p)18F and 18F(p,α)15O reactions: Implications for the level structure of 19Ne, and for 18F production in novae

The largest nuclear physics uncertainty in studies of gamma-ray emission from novae arises from the F-18(p,alpha)O-15 reaction rate that affects the abundance of F-18. Direct measurements have been made of the F-18(p,p)F-18 and F-18(p,alpha)O-15 reaction differential cross sections in the energy range 0.6 <= E-c.m.<= 1.6 MeV. Several resonances have been observed in both measurements, with simultaneous R-matrix fits used to determine the properties of corresponding states in Ne-19. A recently reported state at 7.420 MeV is not seen, while new states are seen including one of J(pi)=3/2(+). A candidate for a recently predicted broad J(pi)=1/2(+) state is seen, which would have significant impact on the low energy F-18(p,alpha)O-15 reaction rate, but its alpha width is significantly smaller than expected.