The ${}^{17}\mathrm{O}$($p,\alpha$)${}^{14}\mathrm{N}$ and ${}^{17}\mathrm{O}$($p,\gamma$)${}^{18}\mathrm{F}$ reactions are of major importance to hydrogen-burning nucleosynthesis in a number of different stellar sites. In particular, ${}^{17}\mathrm{O}$ and ${}^{18}\mathrm{F}$ nucleosynthesis in classical novae is strongly dependent on the thermonuclear rates of these two reactions. The previously estimated rate for ${}^{17}\mathrm{O}$($p,\alpha$)${}^{14}\mathrm{N}$ carries very large uncertainties in the temperature range of classical novae ($T=0.01$–0.4 GK), whereas a recent measurement has reduced the uncertainty of the ${}^{17}\mathrm{O}$($p,\gamma$)${}^{18}\mathrm{F}$ rate. We report on the observation of a previously undiscovered resonance at $E_{c.m.}=183.3$ keV in the ${}^{17}\mathrm{O}$($p,\alpha$)${}^{14}\mathrm{N}$ reaction, with a measured resonance strength $\omega {\gamma }_{p\alpha }=(1.6\pm 0.2)\times {10}^{-3}$ eV. We studied in the same experiment the ${}^{17}\mathrm{O}$($p,\gamma$)${}^{18}\mathrm{F}$ reaction by an activation method, and the resonance strength was found to amount to $\omega {\gamma }_{p\gamma }=(2.2\pm 0.4)\times {10}^{-6}$ eV. The excitation energy of the corresponding level in ${}^{18}\mathrm{F}$ was determined to be $5789.8\pm 0.3$ keV in a Doppler shift attenuation method measurement, which yielded a value of $\tau <2.6$ fs for the level lifetime. The ${}^{17}\mathrm{O}$($p,\alpha$)${}^{14}\mathrm{N}$ and ${}^{17}\mathrm{O}$($p,\gamma$)${}^{18}\mathrm{F}$ reaction rates were calculated using the measured resonance properties and reconsidering some previous analyses of the contributions of other levels or processes. The ${}^{17}\mathrm{O}$($p,\alpha$)${}^{14}\mathrm{N}$ rate is now well established below $T=1.5$ GK, with uncertainties reduced by orders of magnitude in the temperature range $T=0.1$–0.4 GK. The uncertainty in the ${}^{17}\mathrm{O}$($p,\gamma$)${}^{18}\mathrm{F}$ rate is somewhat larger because of remaining obscurities in the knowledge of the direct capture process. These new resonance properties have important consequences for ${}^{17}\mathrm{O}$ nucleosynthesis and γ-ray emission of classical novae.

• Received 26 January 2007

DOI:https://doi.org/10.1103/PhysRevC.75.035810