Experimental study of the level structure in Nb90 and systematics of level structure characteristics near A=90

In beam γ-ray spectroscopic investigations of the ⁹⁰Nb nucleus have been explored by employing the ⁷⁶Ge(¹⁹F,5n)⁹⁰Nb reaction. Twenty-eight new transitions belonging to ⁹⁰Nb have been identified and placed in the proposed level scheme through the analysis of γ-γ coincidence spectra. Shell model calculations have been performed in the restricted π(p3/2,f5/2,p1/2,g9/2)ν(p1/2,g9/2,d5/2,g7/2) configuration space, and compared to the new level scheme. According to the calculations, the newly observed 2614.6 keV γ ray depopulating the (15₃⁺) level at 4421.2 keV is explicated as the breakup of the $N=50$ neutron closed shell, while the γ ray with 2774.0 keV feeding the (13₁^-) level at 2812.9 keV is interpreted as protons excitation across the $Z=38$ subshell.