Spectroscopic Study of the Possibly Triaxial Transitional Nucleus Ge-75

The collective structures of Ge-75 have been studied for the first time via the Ge-74(alpha, 2p1n)Ge-75 fusion-evaporation reaction. Two negative-parity bands and one tentative positive-parity band built on the nu p(1/2), nu f(5/2), and nu g(9/2) states, respectively, are established and compared with the structures in the neighboring N = 43 isotones. According to the configuration-constrained potential-energy surface calculations, a shape transition from oblate to prolate along the isotopic chain in odd-A Ge isotopes is suggested to occur at Ge-75. The properties of the bands in Ge-75 are analyzed in comparison with the triaxial particle rotor model calculations.