The $\beta$ decay of ${}^{97}\mathrm{Sr}$ to ${}^{97}\mathrm{Y}$ has been investigated using ion-guide on-line mass separation and a 10 Ge-detector array to record $\gamma -\gamma$ coincidences to a detection limit well below that of former studies. Similarities are found in the $\beta$-decay patterns of ${}^{99}\mathrm{Zr}$ and of its isotone ${}^{97}\mathrm{Sr}$ and also in the $\gamma$-ray decay rates and branchings of the corresponding levels in their respective daughters ${}^{99}\mathrm{Nb}$ and ${}^{97}\mathrm{Y}$. This indicates a persisting influence of the $d_{5/2}$ neutron shell closure for ${}^{99}\mathrm{Nb}$. The level structure of ${}^{99}\mathrm{Nb}$ and the $\beta$-feeding pattern are discussed in the frame of the interacting boson-fermion plus broken pair model and the microscopic quasiparticle phonon model.

Levels in ${}^{99}\mathrm{Zr}$ populated by $\beta$ decay of on-line mass separated ${}^{99}$Y have been studied by $\gamma$-ray spectroscopic methods, including $\gamma$-$\gamma$ coincidences recorded with an array of ten Ge detectors and level-lifetime measurements. The formerly reported strongly collective character of the 53-keV transition turns out to be questionable. This implies a revision of the experimental evidence for shape coexistence in ${}^{99}\mathrm{Zr}.$ Transition rates and $\gamma$-ray branching ratios make a new level at 679 keV with $t_{1/2}=9\mathrm{}$ ns another candidate for a deformed state.