Study of interference effects in the $^{18}$F$(p,\alpha)^{15}$O

The 18 F(p,α) 15 O reaction plays a crucial role in understanding γ-ray emission from novae.Because of the importance of understanding the 18 F + p reactions, a number of studies of the A=19 isobars have been made using stable and exotic beams.The interference effects among J π = 3 2 + resonances in the 18 F + p system, however, have never been measured, but they can change the S-factor by a factor of 20 at nova energies.R-matrix calculations indicate that the cross sections above the E c.m. = 665 keV resonance are sensitive to the interference between the E c.m. = 8, 38, and 665 keV resonances.In order to study the interference effects, an excitation function for the 1 H( 18 F,α) 15 O reaction has been measured in the energy range of E c.m. = 663-877 keV using radioactive 18 F beams at the Holifield Radioactive Ion Beam Facility.By measuring the 18 F(p,α) 15 O cross section off resonance and comparing the cross section with theoretical calculations, we provide the first experimental constraints on the interference of 3 2 + resonances.