The $^{15}$N($\bm\alpha$,$\bm\gamma$)$^{19}$F reaction and nucleosynthesis of $^{19}$F

Abstract

Several resonances in the $^{15}$N($\alpha$,$\gamma$)$^{19}$F reaction have been investigated in the energy range between 0.6 MeV and 2.7 MeV. Resonance strengths and branching ratios have been determined. High sensitivity could be obtained by the combination of the {\sc{dynamitron}} high current accelerator, the windowless gas target system {\sc{rhinoceros}}, and actively shielded germanium detectors. Two levels of $^{19}$F could be observed for the first time in the ($\alpha$,$\gamma$) channel, and several weak branchings below the detection limits of previous experiments were measured. Two observed resonances correspond to $\alpha$-cluster states in $^{19}$F which have been assigned unambiguously. The astrophysical reaction rate is derived from this set of resonance strengths.