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Study of fusion reactions between heavy nuclei and of the synthesis of super heavy elements by a novel quantum diffusion theory

利用新型量子扩散理论研究重核聚变反应和超重元素的合成

基本信息

批准号：
13640253
负责人：
TAKIGAWA Noboru
金额：
$ 1.73万
依托单位：
Tohoku University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2002
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-13640253/
关键词：
quantum diffusion quantum tunneling super heavy element heavy ion fusion reaction astrophysical nuclear reaction fusion-fission screening effect fluctuation-dissipation theorem チャンネル結合効果

项目摘要

1. We developed a new framework of the coupled-channels calculations to evaluate the cross section of heavy-ion fusion reactions at energies around the Coulomb barrier. The new method replaces the.Woods-Saxon potential in the conventional approach by the double folding potential with the M3Y force as the effective nucleon-nucleon interaction. 2. We applied the method to the ^<16>O+^<154>Sm collisions in order to test its validity, and found that the coupled channels calculations including the ground state rotational band of the target nucleus ^<154>Sm reproduce fairly well the experimental data of the fusion excitation function over a wide energy region -including the Coulomb barrier, though some improvements of the theory are required to explain the experimental fusion barrier distribution. 3. We have then examined whether the method is applicable to heavy-ion collisions between heavy nuclei, where the so called extra-push problem is involved. We studied ^<60>Ni+^<154>Sm scattering as … More an example and found that the calculated barrier transmission cross section well agrees with the experimental data of the total fusion-fission like cross section. 4. It is necessary to develop a theory which can quantitatively describe the process from the inside of the fusion barrier to inside of the fission barrier in order to estimate the fusion cross section between two heavy nuclei such as that for the fusion reactions to synthesize super heavy elements. A diffusion theory has been used as a promising approach to this end under the name of the fluctuation-dissipation dynamics. We have developed a novel quantum diffusion theory by paying attention to the fact that super heavy elements should be synthesized at low temperatures, where a quantum effect due to finite barrier curvature cannot be ignored. Our diffusion equation contains various terms which are absent in the standard diffusion equation by reflecting non-Markovian properties originated from the quantum effects. 5. We applied the quantum diffusion theory to the diffusion process along a potential barrier, and found that while the well known fluctuation dissipation theorem between the diffusion and dissipation coefficients holds at high energies, at low temperatures the deviation from that in the absence of the quantum effect is very different from the known deviation in the diffusion process in a potential well. 6. Through analyses with realistic parameters, we found that both quantum and non-Markpvian effects significantly modify the properties of the diffusion process in synthesizing super heavy elements compared with the results of existing theories. Less

1.我们发展了一个新的耦合通道计算框架，以评估在库仑势垒附近的能量的重离子聚变反应的截面。新方法用双折叠势代替传统方法中的Woods-Saxon势，并以M3 Y力作为核子-核子有效相互作用。2.我们将该方法应用于^<16>O+^<154>Sm碰撞以检验其有效性，发现包括靶核^ Sm基态转动带在内的耦合道计算<154>在包括库仑势垒在内的宽能区上相当好地再现了熔合激发函数的实验数据，尽管需要对理论进行一些改进以解释实验熔合势垒分布。3.然后，我们研究了该方法是否适用于重核之间的重离子碰撞，其中涉及所谓的额外推动问题。我们研究了^<60>Ni+^<154>Sm散射， ...更多信息并发现势垒透射截面的计算值与类聚变-裂变总截面的实验值符合得很好。4.为了估算两重核之间的熔合截面，如合成超重元素的熔合反应截面，需要发展一个能定量描述从熔合势垒内部到裂变势垒内部的过程的理论。一个扩散理论已被用来作为一个有前途的方法，为此目的的名称波动耗散动力学。我们发展了一个新的量子扩散理论，注意到超重元素应该在低温下合成，其中由于有限的势垒曲率的量子效应不能忽略。我们的扩散方程包含了标准扩散方程中不存在的各种项，反映了量子效应引起的非马尔可夫性质。5.我们将量子扩散理论应用于沿着势垒的扩散过程，发现虽然扩散系数和耗散系数之间的涨落耗散定理在高能量下成立，但在低温下，在没有量子效应的情况下的偏离与在势阱中的扩散过程中的已知偏离有很大不同。6.通过对实际参数的分析，我们发现量子效应和非马尔可夫效应对超重元素合成中扩散过程的性质都有显著的影响。少