We report on the observation of a previously unknown resonance at $E_R^{\mathrm{lab}}=194.1\pm 0.6\mathrm{keV}$ in the ${}^{17}\mathrm{O}(p,\alpha ){}^{14}\mathrm{N}$ reaction, with a measured resonance strength $\omega {\gamma }_{p\alpha }=1.6\pm 0.2\mathrm{meV}$. We studied in the same experiment the ${}^{17}\mathrm{O}(p,\gamma ){}^{18}\mathrm{F}$ reaction by an activation method and the resonance-strength ratio was found to be $\omega {\gamma }_{p\alpha }/\omega {\gamma }_{p\gamma }=470\pm 50$. The corresponding excitation energy in the ${}^{18}\mathrm{F}$ compound nucleus was determined to be $5789.8\pm 0.3\mathrm{keV}$ by $\gamma$-ray measurements using the ${}^{14}\mathrm{N}(\alpha ,\gamma ){}^{18}\mathrm{F}$ reaction. These new resonance properties have important consequences for ${}^{17}\mathrm{O}$ nucleosynthesis and $\gamma$-ray astronomy of classical novae.

• Received 22 April 2005

DOI:https://doi.org/10.1103/PhysRevLett.95.031101