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. 我们开发了一种新的耦合通道计算框架，用于评估库仑势垒附近能量下重离子聚变反应的截面。新方法用双折叠势取代了传统方法中的伍兹-撒克逊势。 2. 我们将该方法应用于^<16>O+^<154>Sm 碰撞以测试其有效性，结果发现：包括目标核^<154>Sm的基态旋转带在内的耦合通道计算很好地再现了宽能量区域（包括库仑势垒）上聚变激发函数的实验数据，尽管需要对理论进行一些改进解释实验聚变势垒分布。然后我们检查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力问题。 ^<60>Ni+^<154>Sm 散射为例，发现计算出的势垒透射截面与全聚变裂变截面的实验数据非常吻合。 4. 有必要发展一种理论。它可以描述从聚变势垒内部到裂变势垒内部的过程，从而估计两个重核之间的聚变定量截面，例如合成超重元素的聚变反应的扩散理论。我们通过关注超重元素应在低温下合成的事实，开发了一种新颖的量子扩散理论，其中由于有限的量子效应。势垒曲率不能被忽略。我们的扩散方程包含了标准扩散方程中没有的各项，反映了源自量子效应的非马尔可夫特性。 5.我们将量子扩散理论应用于沿势垒的扩散过程，并且发现虽然众所周知的波动扩散和耗散系数之间的耗散定理在高能、低温下成立，在没有量子效应的情况下的偏差与势阱中扩散过程的已知偏差有很大不同 6. 通过使用实际参数进行分析。，我们发现与现有理论的结果相比，量子效应和非马克普夫效应都显着改变了合成超重元素的扩散过程的性质。