On the Mechanism of Signature Inversion in the Doubly Odd Nuclei

Several mechanisms have been proposed for signature inversion in the structure of A ∼ 80 odd-odd nuclei, but the corresponding theoretical calculations have not been conclusive. In the present work, the angular momentum projected shell model (PSM) is applied to the study of the nuclei Rb. The results of the calculations regarding the positive parity yrast band for the configuration πg9/2 ⊗ νg9/2 and the negative parity yrast band for the configuration π(p1/2 or p3/2 or f5/2)⊗νg9/2 are compared with experimental data. According to the interpretation provided by the projected shell model, the signature inversion displayed in the positive parity yrast band for these nuclei is a signal of a substantial quadrupole shape change that takes place with increasing spin: The nucleus evolves from a prolate shape at low spin through a triaxial shape to an oblate shape at high spin. In addition, we specify the nuclear shapes of these two bands in these two nuclei.