High-spin states in 187Pt were studied via the 173Yb(18O,4n) reaction. Rotational bands based on the νi13/2,ν7/2-[503],νi213/2νj,ν3/2-[512] and ν1/2-[521] configurations were observed,and interpreted within the framework of the cranked shell model. The TRS calculations show that the νi13/2 band has an appreciable negative γ deformation,and the negative-parity bands tend to have a near prolate shape with small positive γ values. Experimental values of B(M1) /B(E2) ratios have been extracted and compared with theoretical values from the semi-classical D-nau and Frauendof approach,strongly suggesting a low frequency πh9/2 alignment in the ν7/2-[503] band.
The level structure of ^19Opt has been studied experimentally using the ^176yb （^18O, 4n） reaction at beam energies of 88 and 95 MeV. γ-γ-t coincidence measurements were carried out. Based on the analysis of T-T coincidence relationships, the level scheme of ^190Pt is extended to high-spin states. A new structure built on the 3413.6 keV 14＋ state has been observed, and the ＂vi13/2^-2 vh9/2^-1 vj （j = P3/2 or f5/2） configuration is tentatively assigned to it.
Signature inversion in odd-odd nuclei is investigated by using a proton and a neutron coupling to the coherent state of the core. Two parameters are employed in the Hamiltonian to set the energy scales of rotation,neutron-proton coupling and their competition. Typical level staggering is extracted from the calculated level energies. The calculation can approximately reproduce experimental signature inversion. Signature inversion is attributed to the rotational motion and neutron-proton residual interaction having reversed signature splitting rules. It is found signature inversion can appear at axially symmetric shape and high-K band.
LIU Min-liang,ZHANG Yu-hu,ZHOU Xiao-hong,GUO Ying-xiang,LEI Xiang-guo,GUO Wen-tao(Institute of Modern Physics,Chinese Academy of Sciences,Lanzhou 730000,China)
