Proton-induced reactions onY89

The reactions ${}_{}{}^{89}{}_{}{}^{}\mathrm{Y}(p, t){}_{}{}^{87}{}_{}{}^{}\mathrm{Y}$, ${}_{}{}^{89}{}_{}{}^{}\mathrm{Y}(p, d){}_{}{}^{88}{}_{}{}^{}\mathrm{Y}$, and ${}_{}{}^{89}{}_{}{}^{}\mathrm{Y}(p, \alpha ){}_{}{}^{86}{}_{}{}^{}\mathrm{Sr}$ are studied with 27.8-MeV protons and solid-state-detector telescopes. A recent revision of the mass of ${}_{}{}^{87}{}_{}{}^{}\mathrm{Y}$ is confirmed. Angular distributions are obtained for the observed states. Several new levels are found in ${}_{}{}^{87}{}_{}{}^{}\mathrm{Y}$. The states at 0.98, 1.85, and 2.09 MeV are assigned $J^{\pi }={\frac{3}{2}}^{-}, {\frac{1}{2}}^{-}, \mathrm{and} {\frac{3}{2}}^{-}$, respectively. In ${}_{}{}^{89}{}_{}{}^{}\mathrm{Y}$, the existence of two low-spin states of opposite parity is established at 0.705 MeV. Distorted-wave Born-approximation (DWBA) calculations are carried out for the ($p, d$) and ($p, t$) data. Good fits to the data are obtained for the ($p, d$) reaction, but the $l=4\mathrm{}$ and $l=1\mathrm{}$ summed strengths deviate in opposite directions from the sum rules. Poor fits are obtained for $L=0\mathrm{}$ transitions in the ($p, t$) reaction on ${}_{}{}^{89}{}_{}{}^{}\mathrm{Y}$ and the experimental $L=2\mathrm{}$ angular distributions show features that are not reproduced by the DWBA. Multistep contributions are suggested. The data for the ($p, \alpha$) reaction show some evidence for direct-reaction processes, but DWBA calculations cannot be carried out.