Signature splitting inversion and backbending in Rb

He, C.*; Shen, S.*; Wen, S.*; Zhu, L.*; Wu, X.*; Li, G.*; Zhao, Y.*; Yan, Y.*; Bai, Z.*; Wu, Y.*; Li, Y.*; Li, G.*; Yan, S.*; Oshima, Masumi*; Toh, Yosuke  ; Osa, Akihiko; Koizumi, Mitsuo; Hatsukawa, Yuichi; Matsuda, Makoto; Hayakawa, Takehito

High-spin states of Rb are studied via the fusion-evaporation reactions Cu+F, Zn+O, and Zn+O with the beam energies of 75 MeV, 76 MeV, and 80 MeV, respectively. Twenty-three states with twenty-eight transitions are added to the previously proposed level scheme, where the second negative-parity band is significantly pushed up to spins of 22 and 15 and two sidebands are built on the known first negative-parity band. Two successive band crossings with frequencies 0.51 MeV and 0.61 MeV in the = 0 branch as well as another one in the =1 branch of the second negative-parity band are observed. Signature inversions occur in the positive-parity and first negative-parity bands at the spins of 11 and 16, respectively. The signature splitting is seen obviously in the second negative-parity band, but the signature inversion is not observed. It is also found that the structure of the two negative-parity bands is similar to that of its isotone Y. Signature inversion in the positive-parity yrast band with configuration g9/2 g9/2 in this nucleus is discussed using the projected shell model.