高激发^(213)Fr核的形变研究  

Investigation of Nuclear Deformation in Excited^(213)Fr

作　　者：张保国[1] 王素芳[1] 段利敏[1] 文万信[1] 靳根明[1] 李祖玉[1] 贺智勇[1] 王宏伟[1] 肖志刚[1] 郑纪文[1] 吴和宇[1] 魏志勇[1] 

机构地区：[1]中国科学院近代物理研究所,兰州730000

出　　处：《高能物理与核物理》2001年第7期636-642,共7页High Energy Physics and Nuclear Physics

基　　金：国家自然科学基金 ( 197750 54 ) ;中国科学院"九五"基础重大科学基金 (KJ95T - 0 3) ;国家重点基础研究发展规划 (G2 0 0 0 0 774

摘　　要：对 132MeV16O +197Au反应产生的裂变碎片和巨偶极共振γ射线进行了符合测量 ,得到了E =92MeV的高激发2 13 Fr的γ衰变谱和γ角关联谱 .观测到复合核巨偶极共振γ角关联谱存在很大的各向异性 .利用改进的统计模型程序分析了实验数据 ,不考虑裂变延迟时 ,统计模型计算可以很好拟合地实验结果 .通过对γ角关联谱的理论计算与实验结果的比较 ,可以得出高激发2 13 Fr核(E =92MeV)Angular correlations between γ rays and fission fragments were measured for the reaction 16 O+ 197 Au at 132MeV. The probability of giant dipole resonance γ rays emission relative to the spin axis of the compound system was extracted by using the correlations,which give direct information about nuclear deformation. Large anisotropy observed in the γ rays energy region of the compound nucleus giant dipole resonance demonstrates unambiguously a deformed shape of the 213 Fr compound system at excitation energies of 92MeV. The fission coincidence γ ray spectra were fitted consistently in terms of the statistical γ ray decay of the compound system and excited fission fragments. The giant dipole resonance parameters obtained from the fits were then used to compute the γ ray angular distributions with respect to the compound nucleus spin axis for prolate and oblate shapes. The comparation between the calculation and the experimental results at excitation of 92MeV show that the 213 Fr nucleus is in the transition from a collective prolate to a noncollective oblate shape.

关 键 词：巨偶极共振 角关联谱 形变跃迁 重离子熔合 核形变 ^213Fr 裂变碎片 γ射线 HIRFL 

分 类 号：O571.22[理学—粒子物理与原子核物理]