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

1.我们发展了一种新的耦合通道计算框架，用于计算库仑势垒附近能量下重离子聚变反应的截面。新方法用双折叠势代替传统方法中的伍兹-萨克森势，并用M3Y力作为核子-核子间的有效相互作用。2.为了验证该方法的有效性，我们将该方法应用于^&lt；16&gt；O+&lt；154&gt；Sm碰撞，发现包括靶核^&lt；154&gt；Sm基态转动带在内的耦合通道计算很好地再现了包括库仑势垒在内的较宽能量范围内聚变激发函数的实验数据，尽管理论需要改进以解释实验中的聚变势垒分布。3.然后，我们考察了该方法是否适用于重核之间的重离子碰撞，其中涉及到所谓的额外推动问题。我们用…研究了^&lt；60；Ni+；154&gt；Sm散射进一步举例，发现势垒传输截面的计算结果与总聚变-裂变截面的实验数据符合得很好。4.为了估算两个重核之间的聚变截面，如合成超重元素的聚变反应，有必要建立一个能够定量描述从聚变势垒内部到裂变势垒内部的过程的理论。在涨落耗散动力学的名义下，扩散理论已被用作这一目标的一种有前途的方法。我们发展了一种新的量子扩散理论，通过注意超重元素应该在低温下合成的事实，其中有限势垒曲率的量子效应是不能忽略的。我们的扩散方程包含了标准扩散方程中所没有的各种项，反映了源于量子效应的非马尔可夫性质。5.将量子扩散理论应用于势垒扩散过程，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下成立，但在低温下，与没有量子效应时的偏差与势垒中扩散过程的已知偏差有很大的不同。6.通过对实际参数的分析，发现与现有的理论结果相比，量子效应和非马尔可夫效应都显著地改变了超重元素合成中扩散过程的性质。较少

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