Y87States Populated by Single-Proton Stripping

The ${}_{}{}^{86}{}_{}{}^{}\mathrm{Sr}({}_{}{}^3{}_{}{}^{}\mathrm{He},d){}_{}{}^{87}{}_{}{}^{}\mathrm{Y}$ reaction was studied at a laboratory beam energy of 20 MeV to test the possible closed-subshell behavior of the 38-proton configuration. The ground-state $Q$ value is found to be 0.346 ± 0.015 MeV. Several new states were identified below an excitation energy of 3.45 MeV. A distorted-wave analysis was used to assign $l$ values for the stripping transitions. Spectroscopic strengths agree well with sum-rule expectations for the $2p$, $1f$, and $1g_{\frac{7}{2}}$ configurations. Comparison with the results of Picard and Bassani for the ${}_{}{}^{88}{}_{}{}^{}\mathrm{Sr}({}_{}{}^3{}_{}{}^{}\mathrm{He},d){}_{}{}^{89}{}_{}{}^{}\mathrm{Y}$ reaction indicates qualitative agreement with shell-model expectations for $2p$ and $1g$ strengths but significant deviations for $1f$ strength and for low-lying $2d$ strength.