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

在该项目的早期阶段，已被证明在重离子聚变反应中识别和选择反应通道的硅探测器阵列(Si Ball)已被改进，以适应在强束流下的高负荷使用。NORDBALL和改进的Si Ball的组合系统在A=80 90的新形变区的光谱研究中取得了巨大的进展。由此建立了包括高激发态在内的核素^&lt；87&gt；Mo，^&lt；87&gt；Nb，^&lt；85&gt；Nb，^&lt；82&gt；Y，^&lt；81&gt；Y，^&lt；82&gt；Zr和^&lt；82&gt；Sr的新能级结构，并对其核性质进行了分析。该区域的形变随着核子数向Z和N=40方向的增加而增大。发现N=46的同位素位于球状核区和形变核区之间，而N=45和46的核在高激发高自旋态下似乎发生了强烈的形变。这些实验结果与摇动模型计算的结果进行了比较。除了上述日本-NBI合作的研究外，九州大学串列加速器实验室还进行了大量实验，以阐明A=80-90区原子核的低激发态和基态性质。丰硕的成果，包括新同位素的系统发现，不仅为高激发下的高自旋态提供了补充信息，而且还导致了一种新的有效方法的发展，以收集这些核的全面光谱知识。

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.