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19F+93Nb耗散反应产物激发函数中截面测量的不重复性 总被引:1,自引:0,他引:1
完成了19F+93Nb重离子耗散碰撞激发函数的两次独立测量.束流的入射能量为100—108MeV,步长250keV.两次测量的宏观条件几乎完全一样,惟一的差别是使用了厚度分别为70和71μg/cm2的两块93Nb同位素靶.实验结果表明:(1)两次测量所得到的耗散反应产物激发函数的涨落具有不可平滑的结构;(2)这种不平滑的涨落截面有不重复的迹象.着重从实验的角度对这一结果进行了讨论. 相似文献
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19F+93Nb重离子耗散碰撞中截面测量的不可重复性 总被引:1,自引:0,他引:1
完成了19F+93Nb重离子耗散碰撞激发函数的两次独立测量.束流19F8+的入射能量100—108MeV,能量步长250keV;两次测量中分别使用了厚度为70和71μg/cm2的93Nb靶,其它宏观实验条件(例如,入射能量及能量步长,探测器及其探测角度,加速器、电子学以及数据获取系统的参数选取等等)则保持完全相同.实验结果表明,两次测量所得到的耗散产物截面的激发函数的不平滑结构具有不可重复性.这一实验结果支持了最近提出的理论预言:“在复杂量子碰撞中存在对初始条件的极端敏感性与混沌运动.” 相似文献
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在中国原子能科学研究院的HI-13串列静电加速器上完成了114MeV和118.75MeV的19F+27Al耗散反应产物B, C, N, O, F, Ne, Na和Mg的微分截面测量. 条形27Al同位素靶的大小尺寸为10mm×50mm, 平均
厚度约67μg/cm2. 固定入射束流19F的能量, 通过移动靶位, 先后轰击了靶上20个不同的位置.实验结果表明, 在弹靶系统、入射能量以及探测系统都相同的多次独立的微分截面测量中, 截面的涨落不呈现高斯型几率分布. 截面测量的这种不重复现象难以用有限计数率的统计性质来解释. 相似文献
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使用离线γ测量技术在实验室系28.3MeV至45.7MeV的能区首次测量了12C+93Nb反应产生的8个核素及同质异能态的激发函数.使用包括非弹性激发和α转移道的简单耦合道模型,结合统计蒸发程序对实验结果进行拟合.计算结果能较好地重现强截面的中子蒸发道(xn)的激发函数.而对于弱的质子(xpyn)特别是α粒子(xαyn)蒸发道的截面,实验测量明显高于模型计算结果.α转移道与入射道耦合作为熔合反应的门庭态使垒下能区重离子熔合截面有很大的加强,实验测量与理论计算的比较表明对于12C+93Nb反应系统在垒下能区可能存在着很强的α转移截面. 相似文献
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Non-Reproducibility of the Cross Sections of the Products Induced from Dissipative Reaction of 17F+27Al
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HAN Jian-Long WANG Qi DONG Yu-Chuan LI Song-Lin DUAN Li-Min WU He-Yu XU Hua-Gen CHEN Ruo-Fu XU Hu-Shan BAI Zhen LI Zhi-Chang LU Xiu-Qin ZHAO Kui 《中国物理C(英文版)》2006,30(2):108-112
The differential cross sections of the dissipative products B, C, N, O, F, Ne, Na and Mg induced from the reactions of 19F+27Al at two incident energies have been measured at the HI-13 tandem accelerator, Beijing. In the case of a fixed beam incident energy 114MeV or 118.75MeV respectively, identical reaction system and the same detection system, 20 target points in steps of 2mm on a 10mm×50mm rectangular Al foil have been bombarded. The experimental results indicate that the probability distribution of the cross sections is much wider than a standard Gaussian distribution. This non-reproducibility of the cross sections can't be interpreted by the statistical property of a finite count rate. 相似文献
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《Nuclear Physics A》1987,464(3):497-524
The time development of fission in highly excited Pb nuclei has been studied by the crystal blocking technique. Thin Ta crystals were bombarded with 19F ions in the energy range 90–120 MeV and the yield of fission fragments was measured for emission directions close to a strong axis. The experimental blocking dips are compared with calculated dips containing a superposition of two components, corresponding to short- and long-lived compound nuclei. The information extracted is the energy dependence of the relative amount of fission which comes from compound nuclei with lifetimes of τ≳3 × 10−17s. The total fission cross section and angular distribution of fission fragments were also measured for 19F bombardment of 181Ta in the energy range 84.3–114.7 MeV and for 16O bombardment of 184W in the energy range 83.4–107.9 MeV. The results of the three types of measurements have been interpreted through comparison with statistical model calculations that follow the spin and energy distribution of compound nuclei through the neutron evaporation cascade. The 19F + 181Ta measurements, when compared with the present 16O + 184W cross section and angular distribution measurements and earlier lifetime measurements for 16O + W, yield information on the spin distribution for the compound nucleus and its influence on the fission process. 相似文献
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YAN Yu-Liang SUN Xiao-Jun ZHANG Yue ZHANG Jing-Shang 《理论物理通讯》2007,47(1):102-106
A new light nuclear reaction model has been developed and the double-differential measurements of lp shell nuclei have been analyzed successfully. Now, the application of this model is expanded to 19F of the 2s-ld shell nucleus. The double-differential cross section of total outgoing neutron for n +^19F reactions at En=14.2 MeV has been calculated and analyzed, which agrees fairly well with the experimental measurements. In this paper, the contributions from different reaction channels to the double-differential cross sections have been analyzed in detail. The calculations indicate that this light nudear reaction model is also able to be used for the 2s-ld shell nucleus so long as the related level scheme couM be provided sufficiently. 相似文献
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WANG Qi TIAN Wen-Dong LI Song-Lin JIANG Zhong-He DONG Yu-Chuan LI Zhi-Chang LU Xiu-Qin ZHAO Kui FU Chang-Bo LIU Jian-Cheng JIANG Hua HU Gui-Qing 《中国物理C(英文版)》2002,26(2):141-147
Two independent measurements of excitation functions in the dissipative collisions of 19F+93Nb have been performed at incident energies from 100 to 108 MeV in steps of 250 keV. The two measurements differed by the thickness of the target foils, 70μg/cm2 and 71μg/cm2, respectively. All the other experimental conditions, the accelerator, the incident energies and steps, the scattering chamber, the detection system, the electronics, the acquisition system and all the parameters selected in the two measurements, were kept to be identical in both experiments. The data indicate non-reproducibility of the non-self averaging oscillating yields in the two independent measurements. The indication of the non-reproducibility of the cross sections is discussed. 相似文献
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《Nuclear Physics A》1997,624(2):242-256
In an experiment performed at the FRS of GSI, we measured total interaction cross sections for 7Be, 8B, and 9C, one-proton-removal cross sections for 8B and 9C as well as two-proton-removal cross sections for 9C on targets ranging from carbon to lead at an energy of 285 MeV/nucleon. In addition, we performed measurements at 142 MeV/nucleon for 8B. The experimental results are compared to different calculations. Glauber-type calculations with different model·density distributions show that, down to incident energies of about 50 MeV/nucleon, total interaction cross-section measurements with light targets are not sensitive to an extended proton distribution in 8B. However, at lower incident energies, a tail in the proton density distribution is needed to explain the total interaction cross sections. Total interaction cross-section measurements with high-Z targets in the present experiment show a significant increase of the cross sections due to low-lying electromagnetic strength. 相似文献
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根据中子与原子核U及其同位素反应的总截面,去弹性散射截面和弹性散射角分布的实验数据,获得了入射中子能量0.1—20MeV的一组普适中子与U及其同位素反应的光学模型势参数.应用光学模型,核裂变理论,耦合道理论,扭曲波玻恩近似理论,宽度涨落修正的Hauser-Feshbach理论和预平衡反应的激子模型,计算和分析了中子与238U反应的所有截面、角分布、能谱和双微分截面.理论计算与实验数据进行了分析比较 相似文献
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HAN Yin-Lu 《中国物理C(英文版)》2004,28(2):177-180
Based on the new measurements of total, nonelastic, elastic cross section and elastic scattering angular distributions for n+U reactions, a set of neutron optical model potential parameters is obtained in the region of incident neutron energy from 0.1 to 20 MeV. The cross sections, angular distributions, energy spectra and double differential cross sections are calculated and analyzed by optical model, nuclear fission theory, distorted wave Born approximation theory, coupled channel theory, the unified Hauser-Feshbach theory, as well as exciton model. The results indicate that our theoretical model can reasonably analysis n+ 238U reaction data with neutron energy lower than 20 MeV. 相似文献
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Binary coincident fragments from the 63Cu + 197Au reaction at a copper energy of 605 MeV have been studied. Fragment energies were measured and fragment masses determined by a kinematic method. Three types of event are defined by suitable adjacent limits in the mass versus total kinetic energy event space. The angular distributions of cross section, average total kinetic energy and average mass have been determined for each event region. Total cross sections determined in the present experiment are compared to those found at lower bombarding energies. Further information on the sequential fission process has been obtained from measurements of yields of radioactive isotopes resulting from bombardment ofthin and thick targets of Au by 605 MeV Cu ions. 相似文献
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重离子耗散反应产物激发函数研究的新进展 总被引:1,自引:1,他引:0
评述了近两年多来在重离子耗散反应激发函数研究中新的实验结果与理论进展.重点介绍27Al+2 7Al耗散反应产物的长程角度关联以及19F+93Nb耗散反应中截面及其涨落测量的不可重复性. The experimental study and the theoretical development on the structures of excitation functions in dissipative heavy ion collisions last years were reviewed. Especially the long range angular correlation in the reaction of 27Al+ 27Al and the non reproducibility of the cross sections measured in the reaction of 19F+ 93Nb were introduced. The experimental results indicate that the angular coherent width in the dissipative... 相似文献