A new rotational band has been identified and assigned to 188Au for the first time using the 173Yb(19F,4nγ) reaction at the beam energies of 86 and 90 MeV. This band is proposed to be built on the πh9/2 νi13/2 configuration by comparing the band properties with known bands in neighboring nuclei. The prolate-to-oblate shape transition through triaxial shape has been proposed to occur around 188Au for the πh9/2 νi13/2 bands in odd-odd Au isotopes on the basis of total Routhian surface (TRS) calculations.
OSHIMA MTOH YKOIZUMI MKIMURA AHatsukawa YMORIKAWA TNAKAMURA MSUGAWARE MKUSAKARI H
High-spin levels of ^189Pt have been studied with the in-beam T-spectroscopy method via the ^176Yb（^18O,5n） reaction at the beam energies of 88 and 95 MeV. The previously known ＂vi-1 13/2 band has been confirmed, and its unfavored signature branch extended up to the 31/2^＋ state. Within the framework of the triaxial particle-rotor model, the vi-1 13/2 band is suggested to be associated with the 11/2[615] configuration, and to have triaxial deformation.
滑伟周小红张玉虎郭应祥Oshima M.Toh Y.Koizumi M.Osa A.Hatsukawa Y.亓斌张双全孟杰Sugawara M.
High-spin states in nucleus ^139Pm have been studied using the reaction ^116Cd（^27Al, 4n）^139Pm. Two dipole cascades have been found. Spin and parity assignments were based on the Directional Correlation of Oriented Nuclei （DCO） ratios and systematic behavior in neighboring odd-proton nuclei. The level structures of ^139Pm are compared with those of the N = 78 isotone ^141Eu in which two dipole bands have been confirmed as magnetic rotational bands. The close similarity between them suggests that the dipole bands in ^139Pm may be magnetic rotational bands.
High-spin states of ^165Er were studied using the ^160Gd（^9Be, 4n）reaction at beam energies of 42 and 45 MeV. The previously known bands based on the ν5/2^-[523] and ν5/2^＋[642] configurations have been extended to high-spin states. Electric-dipole transitions linking these two opposite parity bands were observed. Relatively large B（E1） values have been extracted experimentally and were attributed to octupole softness.
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)
