Simultaneous measurement of the 18F(p,p)18F and 18F(p, )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 18 F(p,α) 15 O reaction rate that affects the abundance of 18 F. Direct measurements have been made of the 18 F(p,p) 18 F and 18 F(p,α) 15 O 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 19 Ne. A recently reported state at 7.420 MeV is not seen, while new states are seen including one of J π = 3/2 + . A candidate for a recently predicted broad J π = 1/2 + state is seen, which would have significant impact on the low energy 18 F(p,α) 15 O reaction rate, but its alpha width is significantly smaller than expected.