Y89(t, p)Y91reaction atEt=20MeV

The reaction ${}_{}{}^{89}{}_{}{}^{}\mathrm{Y}(t, p){}_{}{}^{91}{}_{}{}^{}\mathrm{Y}$ has been measured at an incident energy of 20 MeV. Differential cross sections were measured at 13 angles and an excitation range of 5 MeV was observed with 18 keV resolution. The data are compared to distorted wave calculations both for $L$ assignments and magnitude relations. Sixteen new levels are reported in ${}_{}{}^{91}{}_{}{}^{}\mathrm{Y}$ as well as many new limits on spin assignments. An interpretation of the results as a proton hole coupled to ${}_{}{}^{92}{}_{}{}^{}\mathrm{Zr}$ pairing-multipole states is presented. Such an analysis provides a qualitative description of the observed strength, but a more complex analysis is required for quantitative results.