Seniority scheme for <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>j</mml:mi> <mml:mo>=</mml:mo> <mml:mn>9</mml:mn> <mml:mo>/</mml:mo> <mml:mn>2</mml:mn> </mml:mrow> </mml:math> nuclear orbitals

Experimental $B(E2)$ reduced transition strengths in $N=50$, 126 and $Z=82$ semimagic nuclei are compared to the values predicted by the seniority scheme for a single $j=9/2$ orbital. For the first time all available data, both on even- and odd-mass nuclei, were considered in the same framework. The seniority scheme provides a good approximation for all these three regions with the best fit given by the lead isotopes. In addition, shell model calculations using well-established interactions were performed. In the $N=50$ and $Z=82$ nuclei considering all orbitals within a shell provide only a limited improvement in reproducing the data when compared to the seniority scheme. In contrast, the shell model provides much better agreement for $N=126$ nuclei, where the $\ensuremath{\pi}{f}_{7/2}$ orbital has increasing effect on the transition strengths as the $j=9/2$ orbital is filled. In order to further test the applicability of the seniority scheme in the lead isotopes, and investigate the possible distorting effect of the $\ensuremath{\nu}{i}_{11/2}$ orbital, more experimental information is required, especially for $^{214,215,216}\mathrm{Pb}$.