(He3,α) Reaction onY89andKr86at 18 MeV

Neutron hole states in $N=49\mathrm{}$ nuclei were studied with the (${}_{}{}^3{}_{}{}^{}\mathrm{He}$, $\alpha$) reaction on ${}_{}{}^{89}{}_{}{}^{}\mathrm{Y}$ and ${}_{}{}^{86}{}_{}{}^{}\mathrm{Kr}$. Spectroscopic information was obtained from a distorted-wave Born-approximation analysis. Various optical potential wells were used. The results were compared and found to be in good agreement with each other. In ${}_{}{}^{88}{}_{}{}^{}\mathrm{Y}$, the ground state and the first excited state (0.40 MeV) are excited by $1g_{\frac{9}{2}}$ neutron pickup. The coupling of the unpaired $2p_{\frac{1}{2}}$ proton to the $1g_{\frac{9}{2}}$ neutron hole yields $4^{-}$ and $5^{-}$ states. Assuming that these two states represent the total $T<\mathrm{}{g}_{\frac{9}{2}}$ neutron pickup strength in ${}_{}{}^{89}{}_{}{}^{}\mathrm{Y}$, the sum of their spectroscopic factors is normalized to 10. Using the same normalization factor for ${}_{}{}^{85}{}_{}{}^{}\mathrm{Kr}$ states, the spectroscopic factor for the ground state excited by $1g_{\frac{9}{2}}$ neutron pickup represents only 60% of the total $T<\mathrm{}{g}_{\frac{9}{2}}$ neutron pickup strength. Two other possible ${\frac{9}{2}}^{+}$ neutron hole states were observed at 1.89- and 2.03-MeV excitation. Spectroscopic information about other neutron hole states observed is also presented.