^(135)La高自旋态的实验研究

Experimental Observation of High Spin States in ^(135)La Nucleus

利用在束γ谱实验技术 ,通过 12 8Te(10 B ,3n) 13 5La反应研究了 13 5La的高自旋态 .基于γ γ符合关系、γ射线的相对强度和各向异性度的测量结果 ,建立了 13 5La的能级纲图 .在ω≈ 0 .4 0MeV附近 ,观测到基于πh11 2 质子轨道上的负宇称带的带交叉 .比较N =78同中子素链能级结构的系统性 ,认为该带交叉是由一对h11 2 准质子发生转动顺排造成的 .在高自旋态处 ,观测到具有很强M1跃迁、Signature劈裂很小的ΔI =1负宇称带 ,根据系统性认为该带是建立在πh11 2 (νh11 2 ) 2 组态上的γ≈ - 6 0°的扁椭球形变带 .

High spin states of 135La have been experimentally studied by using 128Te(10B, 3n) 135La reaction at 46 MeV beam energy. Based on the γ-γ coincidence relationships, relative intensities and ADO ratios, a level scheme of 135La has been established. Both signature components of the πh-11/2 negative-parity band and a band crossing at ω≈0 40MeV were observed. In view of the systematics of the N=78 isotones, this backbending is proposed to be caused by the alignment of a pair of πh-11/2 protons. The πh-11/2 protons drive the nuclear core towards γ≈0°, the collective prolate shape. In addition, a ΔI=1 negative-parity band with strong M1 transitions and a very small signature splitting was observed. Comparing with the systematic features of ΔI=1 bands in neighboring odd-proton nuclei in this mass region, the πh-11/2(νh-11/2)2 configuration was assigned to the ΔI=1 bands of 135La. The alignment of the h-11/2 neutron pair drives the nuclear core towards γ≈-60°, the collective oblate shape.