The high-spin level structures of the ${}^{96,97}\mathrm{Nb}$ isotopes have been studied. The isotopes were produced in the fission of the compound systems formed in two heavy-ion-induced reactions, ${}^{24}\mathrm{Mg}$ (134.5 MeV) $+$ ${}^{173}\mathrm{Yb}$ and ${}^{23}\mathrm{Na}$ (129 MeV) $+$ ${}^{176}\mathrm{Yb}$. Gamma-ray spectroscopy was accomplished with the Gammasphere array. High-spin states are observed for the first time in both isotopes with excitation energies up to 5.2 and 6.6 MeV in ${}^{96,97}\mathrm{Nb}$, respectively. The coupling of the odd proton occupying the $g_{9/2}$ orbital to the yrast states in the subshell closure nucleus of ${}^{96}\mathrm{Zr}$ can account for the first excited states of ${}^{97}\mathrm{Nb}$. A comparison with the first excited states in ${}^{95}\mathrm{Zr}$ is also attempted. The addition of a neutron hole in ${}^{96}\mathrm{Nb}$ results in a much more fragmented level scheme.

• Received 6 August 2010

DOI:https://doi.org/10.1103/PhysRevC.82.044306