Two-Hole Multiplets inY88fromY89(d, t)andZr90(d, α)Studies

States of ${}_{}{}^{88}{}_{}{}^{}\mathrm{Y}$ up to 2 MeV in excitation were studied with 8-12-keV resolution by ($d$,$t$) and ($d$,$\alpha$) experiments, and interpreted in terms of two-hole configurations. ${}_{}{}^{89}{}_{}{}^{}\mathrm{Y}(d, t)$ angular distribution and spectroscopic factors were obtained at 14.0- and 15.75-MeV bombarding energy. Six low-lying levels not detected in earlier (${}_{}{}^3{}_{}{}^{}\mathrm{He}$,$\alpha$) experiments were resolved. The summed spectroscopic ($C{}_{}{}^2{}_{}{}^{}S$) strength obtained for the five strong $l=1\mathrm{}$ transitions was $\frac{2}{3}$ of the sum-rule limit in contrast to previous (${}_{}{}^3{}_{}{}^{}\mathrm{He}$,$\alpha$) results which exceeded it. Successful distorted-wave Born-approximation (DWBA) predictions for ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}(d, \alpha ){}_{}{}^{88}{}_{}{}^{}\mathrm{Y}$ angular distributions permitted the assignment of 15 $L$ values and corresponding $J^{\pi }$ limits for the final states, about half of which had not been resolved in previous particle-transfer work. Levels dominated by ${\left(f_{\frac{5}{2}}{g}_{\frac{9}{2}}\right)}^{-1\mathrm{}}$ and ${\left(p_{\frac{3}{2}}{g}_{\frac{9}{2}}\right)}^{-1\mathrm{}}$ configurations were identified by comparison with previous data for ${}_{}{}^{86}{}_{}{}^{}\mathrm{Rb}$. Higher-spin states dominated by the ${g_{\frac{9}{2}}}^2$ configuration were not seen, as expected; however, a comparison of measured and "absolute" microscopic DWBA cross sections for known two-hole states showed evidence of strong configuration mixing. Additional evidence for a $2^{-}$,($2^{+}$) doublet at 706 keV excitation was found.