Investigation of the level structure of ⁹⁰Nb nucleus using the shell model

Shell model calculations have been carried out for ⁹⁰Nb nucleus with the model space in which the valence protons occupy the f_5/2, p_3/2, p_1/2, and g_9/2 orbitals and the valence neutrons occupy the p_1/2, g_9/2, d_5/2, and g_7/2 orbitals. According to the calculated results, the negative parity is from the contribution of the proton of the f_5/2, p_3/2, and p_1/2 orbits. The moderate spin states of ⁹⁰Nb are mainly due to the excitation of protons from the f_5/2 and p_3/2 orbits to the p_1/2 and g_9/2 orbits across the Z = 38 subshell closure, and the high spin states arise from the excitation of a single neutron from the g_9/2 orbit into the d_5/2 orbit across the N = 50 shell closure.