Abstract
Experimental B(E2) reduced transition strengths in N=50, 126 and Z=82 semi-magic nuclei are compared to the values predicted by the seniority scheme for a single j = 9/2 orbital. For the rst 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 t 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 πf 7/2 orbital has increasing eect on the transition strengths as the j = 9/2 orbital is lled. In order to further test the applicability of the seniority scheme in the lead isotopes, and investigate the possible distorting eect of the νi 11/2 orbital, more experimental information is required, especially for 214,215,216 Pb.