Signature inversion in pi h(9/2) circle times nu i(13/2) oblate band of Tl-188

High-spin Level structure of Tl-188 has been studied via Gd-157 (Cl-35,4n) fusion-evaporation reaction at beam energy of 170MeV. A rotational band built on the pi h(9/2) circle times nu i(13/2) configuration with oblate deformation has been established. Spin values have been proposed to the pi h(9/2) circle times nu i(13/2) oblate band based on the similarities between the oblate band of Tl-188 and those in odd-odd Tl190-200. With the spin assignments, the low-spin signature inversion has been revealed for the pi h(9/2) circle times nu i(13/2) oblate band of Tl-188. The low-spin signature inversion can be interpreted qualitatively in the framework of the quasi-particles plus rotor model including a J dependent p-n residual interaction.