Proton-induced reactions onY89

Abstract

The reactions $^{89}\mathrm{Y}(p, t)^{87}\mathrm{Y}$, $^{89}\mathrm{Y}(p, d)^{88}\mathrm{Y}$, and $^{89}\mathrm{Y}(p, \ensuremath{\alpha})^{86}\mathrm{Sr}$ 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 ${J}^{\ensuremath{\pi}}={\frac{3}{2}}^{\ensuremath{-}}, {\frac{1}{2}}^{\ensuremath{-}}, \mathrm{and} {\frac{3}{2}}^{\ensuremath{-}}$, 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 $l=4$ and $l=1$ summed strengths deviate in opposite directions from the sum rules. Poor fits are obtained for $L=0$ transitions in the ($p, t$) reaction on $^{89}\mathrm{Y}$ and the experimental $L=2$ angular distributions show features that are not reproduced by the DWBA. Multistep contributions are suggested. The data for the ($p, \ensuremath{\alpha}$) reaction show some evidence for direct-reaction processes, but DWBA calculations cannot be carried out.NUCLEAR REACTIONS $^{89}\mathrm{Y}(p, d)$, ($p, t$), ($p, \ensuremath{\alpha}$), $E=27.8$ MeV; measured $\ensuremath{\sigma}(E, \ensuremath{\theta})$, $\ensuremath{\theta}=9\ensuremath{-}50\ifmmode^\circ\else\textdegree\fi{}$, $\ensuremath{\Delta}\ensuremath{\theta}=3\ensuremath{-}4\ifmmode^\circ\else\textdegree\fi{}$, resolution 35-60 keV; deduced $^{87}\mathrm{Y}$-$^{88}\mathrm{Y}$ mass difference, $^{87,88}\mathrm{Y}$, $^{86}\mathrm{Sr}$ levels; DWBA analysis, deduced $S$ for $^{88}\mathrm{Y}$.