Evidence of Partial Seniority Conservation in the $\pi{g}_{9/2}$ Shell for the $N=50$ Isotones

The reduced transition probabilities for the $4^+_1 \to 2^+_1$ and $2^+_1 \to 0^+_1$ transitions in $^{92}$Mo and $^{94}$Ru and for the $4^+_1 \to 2^+_1$ and $6^+_1 \to 4^+_1$ transitions in $^{90}$Zr have been determined in this experiment making use of a multinucleon transfer reaction. These results have been interpreted on the basis of realistic shell-model calculations in the $f_{5/2}, p_{3/2}, p_{1/2},$ and $g_{9/2}$ proton valence space. Only the combination of extensive lifetime information and large scale shell-model calculations allowed the extent of the seniority conservation in the $N=50 g_{9/2}$ orbital to be understood. The conclusion is that seniority is largely conserved in the first $\pi{g}_{9/2}$ orbital.