Seniority and configurations in neutron-rich Nickel isotopes *

Excited states in low-energy spectra of Ni are considered. Accordingly, pairing forces in the form of surface delta interaction are employed to account for the formation of the ground state multiplet with seniority states. The multiplet splitting is described with mass relationships of masses of neighboring nuclei. Subsequently, the seniority model is adopted to reproduce or predict the states in odd-even isotopes and in even-even isotopes. The correct account of the state should allow for the description of the reversed order of states with and observed in experiments. The results obtained are compared with the structure of similar multiplets in isotones.