First experimental constraints on the interference of $\frac{3}{2}^{+}$ resonances in the $^{18}$F($p$,$\alpha$)$^{15}$O reaction

The $^{18}$F($p$,$\alpha$)$^{15}$O reaction plays a crucial role in understanding $\gamma$-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 $J^\pi$ = $\frac{3}{2}^{+}$ 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,$\alpha$)$^{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($p$,$\alpha$)$^{15}$O cross section off resonance and comparing the cross section with theoretical calculations, we could provide the first experimental constraints on the interference of $\frac{3}{2}^{+}$ resonances.