Collective rotational bands were observed for the first time in neutron-rich odd–odd 142La by means of γ-γ-γ and γ-γ-γ-γ coincidence measurements of prompt fission γ rays from 252Cf using multi-detector array Gammasphere. Similarity between the yrast band of 142La and those of neighboring 144La, 144Ce was found and interpreted as quasiparticle excitations. PES calculations suggested triaxial deformation for the ground state of 142La. Considerable triaxial and near zero octupole deformations were deduced for the yrast band of 142La by the TRS model calculations. The band-crossing observed in the yrast band of 142La was interpreted to be caused by alignment of the (h11/2)² proton pair, and the crossing frequency was best reproduced by the TRS calculations taking into account triaxial deformations. In contrast to the interpretations for the band crossing of 142La, alignments of the (i13/2)² neutron pair were found to be responsible for the band-crossing of the yrast band in the neighboring even-N 143La, and triaxial degree of freedom was found to play a more significant role than octupole deformations in the nucleus, although its β3 values deduced are large.

中文翻译：

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首次观测到富中子 142La 中的集体旋转带和研究 142,143La 中的八极/三轴变形

首次在富中子奇-奇中观察到集体旋转带142拉通过γ-γ-γ和γ-γ-γ-γ瞬变裂变的巧合测量γ来自的光线252Cf 使用多探测器阵列 Gammasphere。yrast 带之间的相似性142拉和邻近地区144啦啦，144Ce 被发现并解释为准粒子激发。PES 计算表明 142La 基态的三轴变形。对于142La 由TRS 模型计算得出。在 yrast 带中观察到的带交叉142La 被解释为是由 (h11/2) ^{2 个}质子对，考虑到三轴变形，TRS 计算最好地再现了交叉频率。与对带交叉的解释相反142La，对齐（i13/2)发现^{2 个}中子对负责相邻偶数 N 中 yrast 带的带交叉143La 和三轴自由度被发现比原子核中的八极变形发挥更重要的作用，尽管它的β3推导出的值很大。