The uncertain origin of the proton rich Mo and Ru isotopes has motivated cross-section measurements of α- and neutron-induced reactions. The experiments were performed via the activation technique by irradiating thin layers of natural ruthenium with α-particle beams close to the Gamov window of the p process between 7.0 and 10.5 MeV. The cross sections of the reactions ${}^{96}\mathrm{Ru}(\alpha ,\gamma ),$ ${}^{96}\mathrm{Ru}(\alpha ,n),$ ${}^{96}\mathrm{Ru}(\alpha ,p),$ and ${}^{98}\mathrm{Ru}(\alpha ,n)$ could be determined with uncertainties of typically 10%. On average, these results are about two to three times smaller than recent statistical model predictions. Additional activations in a quasistellar neutron spectrum corresponding to $kT=25\mathrm{}\mathrm{keV}$ allowed us to obtain the complementary stellar $(n,\gamma )$ cross sections for ${}^{96}\mathrm{Ru},$ ${}^{102}\mathrm{Ru},$ and ${}^{104}\mathrm{Ru}.$ In these cases the agreement with model calculations is considerably better.

• Received 21 December 2001

DOI:https://doi.org/10.1103/PhysRevC.66.015803