Level structure with high excitation states in¹³⁴Ba

The high spin states in neutron-deficient ¹³⁴Ba nucleus have been studied by using heavy ion induced reaction ¹³⁰Te( ⁹Be,5n) and in-beam γ-ray spectroscopy carried out at China Institute of Atomic Energy. The level scheme has been updated with spin up to 20h. Most of levels and transitions reported in the previous publications have been confirmed. The levels in the ground state band was expanded to 10 ⁺ state, and many levels and transitions above the 10⁺ isomer have been identified. Based on the systematical analyzing, the 10 ⁺ isomer in ¹³⁴Ba is a yrast trap of prolate deformation with γ ≈ 120° which is originated from two neutron configuration. Above the 10⁺ isomer level, the new levels show strong single-particle motion and complex structural characteristics. The obvious collective back-bending has been observed in the ground state band. The CSM calculations indicate that the back-bending of ¹³⁴Ba is caused by alignment of a pair of h_11/2 quasi-neutrons. The nuclear shape has obviously changed with rotational frequency increasing according to the TRS calculations, and the nucleus probably has an oblate deformation with γ≈ -60° after the neutron alignment.