Experimental approach towards shell structure at ¹⁰⁰Sn and ⁷⁸Ni

The status of experimental approach to ¹⁰⁰Sn and ⁷⁸Ni is reviewed. Revised single particle energies for neutrons are deduced for the N=Z=50 shell closure and evidence for low lying I^π=2⁺ and 3^- states is presented. Moderate E2 polarization charges of 0.1 e and 0.6 e are found to reproduce the experimental data when core excitation of ¹⁰⁰Sn is properly accounted for in the shell model. For the neutron rich Ni region no conclusive evidence for an N=40 subshell is found, whereas firm evidence for the persistence of the N=50 shell at ⁷⁸Ni is inferred from the existence of seniority isomers. The disappearance of this isomerism in the mid νg_9/2 shell is discussed.