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Study of Giant resonances in Hot Nuclei produced in Heavy Ion Fusion Reactions

重离子聚变反应产生的热核的巨共振研究

基本信息

批准号：
02640219
负责人：
KASAGI Jirohta
金额：
$ 1.79万
依托单位：
Tokyo Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1990
资助国家：
日本
起止时间：
1990 至 1991
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-02640219/
关键词：
Giant Resonance Hot Nuclei Heavy Ion Reaction Fusion Reaction High Energy gamma rays Level Density Limiting Temperature Statistical Model γ線多重度

项目摘要

1. We have studied properties of hot nuclei by using ^<40>Ar+Ni, ^<92>Mo, and ^<122>Sn reactions with E/A=21 and 26 MeV by using the RIKEN Ring Cyclotron. Fusion reaction process was selected to study level densities and giant dipole resonances in hot nuclei. It was found that neutron energy spectra measured in coincidence with fusion residues were reproduced with the level density parameter a=A/(9<plus-minus>1). However, yields of the GDR decay gamma rays do not increase above E_x-250 MeV. The limiting temperature for the GDR gamma -ray decay were deduced as T_c-17A^<-1/3> for 80 < A < 150. It is highly desirable to continue the systematic study in order to answer the question whether the collective motion of the nucleus disappears at the high temperature or the hot nucleus is cooled down by particle evaporations before it emitts gamma rays.2. In order to investigate the dependence of giant dipole resonances on the excitation energy and the angular momentum, high energy gamma rays were measured in ^<100>Mo+^<32>S reaction with E=150, 180 and 210 MeV using the tandem accelerator at JAERI. The result shows that the GDR width depends strongly on the thermal excitation energy for E_x > 100 MeV and an empirical formula GAMMA =4.5+0.035E_x+1.6x10^<-8>E_x^4 obtained in the previous work at RIKEN can explain the data very well.

1. 在E/A=21和26 MeV条件下，利用RIKEN环形回旋加速器研究了^<40>Ar+Ni、^<92>Mo和^<122>Sn的热核性质。选择聚变反应过程来研究热核中的能级密度和巨偶极子共振。结果表明，与聚变残馀量相符的中子能谱可以用能级密度参数a= a /（9<正负>1）再现。然而，GDR衰变伽马射线的产率在E_x-250 MeV以上不会增加。在80 < A < 150时，GDR γ射线衰变的极限温度为T_c-17A^<-1/3>。为了回答核的集体运动是否在高温下消失，还是热核在发射伽马射线之前被粒子蒸发冷却，继续进行系统的研究是非常必要的。为了研究巨偶极子共振对激发能和角动量的依赖关系，利用JAERI的双列加速器测量了E=150、180和210 MeV的^<100>Mo+^<32>S反应中的高能伽马射线。结果表明，GDR宽度强烈依赖于E_x > 100 MeV的热激发能，RIKEN先前的经验公式GAMMA =4.5+0.035E_x+1.6x10^<-8>E_x^4可以很好地解释这些数据。