High-spin states and shell structure of the odd-odd nucleus ⁹⁰Nb

The high-spin states of the odd-odd nucleus ⁹⁰Nb have been investigated with in-beam γ-spectroscopic techniques via the ⁷⁶Ge(¹⁹F,5n)⁹⁰Nb reaction at a beam energy of 80 MeV. γ-γ coincidences were measured using a γ-ray detector array. Twenty new γ rays have been assigned to ⁹⁰Nb and the level scheme has been extended up to an excitation energy of 8.095 MeV at spin 18ℏ. The level structure of ⁹⁰Nb at high spin states has been well reproduced using semiempirical shell-model calculations in the model space π(1p_1/2,0f_5/2,0g_9/2)ν(0g_9/2). The results show that the excitation of protons plays an important role in generating the high-spin states of ⁹⁰Nb.