Effective nucleon-nucleon interactions in the Y, Zr, Nb, Mo and Tc isotopes

The energy levels of the Nb, Mo and Tc isotopes with a neutron number N between 50 and 56 are first calculated under the assumptions that their protons and neutrons outside Z = 40 and N = 50 are in the 1g _{9 2} and 2d _{5 2} orbits, respectively, and that the effective nucleon- nucleon interactions are given by the experimental spectra of ⁹²Mo, ⁹²Zr and ⁹²Nb. Good agreement with experiment is generally achieved for energy level positions, spectroscopic factors for direct reactions, magnetic and quadrupole moments, M1 and E2 transition probabilities. In order to introduce the influence of the 2p _{1 2} proton orbit in this mass region, the nuclei with 39≦Z≦43 and N = 50 are then investigated and the effective proton-proton interaction in the 2p _{1 2} and 1g _{9 2} orbits is determined; the low-lying levels of these isotopes and five E2 transition probabilities in ⁹⁰Zr and ⁹²Mo are accurately reproduced by these calculations. Using the latter interaction together with effective neutron-neutron and proton-neutron interactions whose validity has been tested earlier, the Y, Zr and Nb isotopes with 51 ≦ N ≦ 56 are then studied taking thoroughly into account the influence of the 2p _{1 2} and 1g _{9 2} proton orbits, and assuming as before that the neutron outside N = 50 are in the 2d _{5 2} orbit. Satisfactory agreement is again generally obtained. Comparison with the previous calculations shows the ability of the effective nucleon-nucleon interactions to absorb the influence of configuration mixings and justifies their use to correlate a large number of experimental data in widely different fields.