Single-particle excitations in 89Y

Inelastic-electron-scattering cross sections have been measured for the first three excitations in ⁸⁹Y at forward angles for momentum transfers of 1.25<q<3.01 fm^-1 and at 180° for 0.72<q<2.67 fm^-1. Transition charge and current densities extracted in a Fourier-Bessel analysis of all existing cross sections show considerable departures from the single-particle model. The inclusion of core polarization from the operator renormalization approximation for shell models gives good agreement with experimental results.