Shell Model and the Levels of Zr 91

A shell-model interpretation of low-lying positive-parity states of ${\mathrm{Zr}}^{91}$ has been attempted by taking into account the residual interactions between the two protons in the $2{p}_{\frac{1}{2}}$ and $1{g}_{\frac{9}{2}}$ configurations coupled to a neutron in the $2{d}_{\frac{5}{2}}$, $3{s}_{\frac{1}{2}}$, $1{g}_{\frac{7}{2}}$, and $2{d}_{\frac{3}{2}}$ single-particle states. A finite-range, central two-body force with a Gaussian radial dependence was assumed. Data on other nuclei in this mass region have been analyzed to provide a set of model parameters. Qualitative agreement has been obtained with the experimental data on ${\mathrm{Zr}}^{91}$.