Study of the Extreme States with High Excitation Energy and High Spin by Ge-Si Crystal Ball.

在项目前期，对在重离子聚变反应中具有很强识别和选择反应通道能力的硅探测器阵列（Si Ball）进行了改进，以适应在大光束电流下的高负荷使用。NORDBALL和改进Si Ball的组合系统使a =80 - 90新变形区的光谱研究取得了重大进展。结果，建立了包含高激发态的^<87>Mo、^<87>Nb、^<85>Nb、^<82>Y、^<81>Y、^<82>Zr和^<82>Sr的新能级结构，并进行了核性质分析。随着核子数向Z和N = 40方向增加，该区域原子核的变形增大。发现N= 46的等音位于球形核区和变形核区之间的边界，N=45和46的核在高激发的高自旋状态下似乎有强烈的变形。实验结果与曲柄模型计算结果进行了比较。除了上述日本- nbi合作的研究外，九州大学的串列加速器实验室也进行了大量的实验来阐明A = 80 -90区域内原子核的低洼态和基态的性质。包括新同位素的系统发现在内的卓有成效的成果不仅为高激发下的高自旋态提供了补充信息，而且还导致了一种收集这些原子核的全面光谱知识的新有效方法的发展。

In the early stage of this project, a silicon detector array (Si Ball) which had proved to be quite powerful in the identifications and selections of the reaction channels in heavy ion fusion reaction was improved to stand the high duty use at high beam currents.The combined system of NORDBALL and the improved Si Ball brought about a dramatic progress in the spectroscopic studies of the new deformed region of A=80 90. As a result, new level structures of nucleides of ^<87>Mo, ^<87>Nb, ^<85>Nb, ^<82>Y, ^<81>Y, ^<82>Zr and ^<82>Sr including highly excited states have been established and the analysis for the nuclear properties have been carried out. The deformation of nuclei in this region grows with the nucleon number toward Z and N = 40. The isotones of N = 46 were found to lie the border between spherical and deformed nucleus regions, and the nuclei of N=45 and 46 seem to be strongly deformed at highly excited high-spin states. These experimental results have been compared with the results of cranking model calculation.Besides the above mentioned studies in Japan-NBI collaboration, lots of experiments have been carried out at the tandem accelerator laboratory of Kyushu University to clarify the properties of low-lying and ground states of the nuclei in the A = 80 -90 region. The fruitful outputs including a systematic discovery of new isotopes not only gave complementary information for the high spin states at high excitation but also led to the development of a new effective method of collecting thorough spectroscopic knowledge of these nuclei.