Single-Neutron-Hole States inZr89from theZr90(He3,α)Zr89Reaction at 18 MeV

The (${\mathrm{He}}^3,\alpha$) single-neutron pickup reaction was studied in ${\mathrm{Zr}}^{90}$ at 18 MeV using solid-state detectors. The reaction $Q$ value was determined to be 8.58±0.05 MeV. Levels observed in this reaction are the ground state, the 0.59-, 1.07-, 1.44-, 1.72-, 1.84-, 2.06-, and 8.10-MeV states. Angular distributions of all these states except the 8.10-MeV state were measured from 10° to 100° in 5° steps. Distorted-wave Born-approximation analysis (DWBA) yielded the following $l$- value assignments: ground state $l=4\mathrm{}$, 0.59-, 1.07-, and 1.84-MeV states, $l=1\mathrm{}$, 1.44- and 2.06-MeV states, $l=3\mathrm{}$; 1.72-MeV state, possibly $l=3\mathrm{}$. Relative spectroscopic factors were extracted. The 8.10-MeV state was identified as the analog state of the ground state of ${\mathrm{Y}}^{89}$. Its angular distribution was measured from 10° to 50° and was in agreement with a ${\mathrm{½}}^{-}$ spin assignment. The Coulomb displacement energy was calculated to be 11.70±0.05 MeV. The ratio of the spectroscopic factors of the $T_{>}$ and the $T_{<}$ states is discussed in connection with the DWBA predictions. The locations of the single-neutron-hole states are investigated.