Macroscopic Quantum Tunneling in Nuclear Reactions and Fission

本项目旨在发展核物理中宏观量子隧穿的理论和数据分析，主要围绕库仑势垒附近和以下能量的重离子聚变反应和裂变。同时开展了弹性重离子散射、不稳定原子核诱导的重离子碰撞、天体物理核反应、相对论平均场理论下的核结构、中能重离子碰撞、微团簇物理等相关课题的研究。主要成果如下：在重离子聚变反应中，通过对^<64>Ni+ 92,96zr和^<16>O+^<112>Cd, ^<144>Sm聚变反应的耦合通道分析，阐明了高阶耦合效应的重要性，并通过描述^<16>O+^<112>Cd, ^<144>Sm与相互作用玻色子模型的聚变，表明了非调和性在振动耦合中的重要作用。作为一个重要的结果，我们的研究表明，核聚变数据提供了关于核的非调和性质的非常有用的信息，激发的振动模式和核的变形符号。对于多自由度系统中的量子隧穿，我们证明了质量重正化在绝热量子隧穿中的重要性，并提出了利用环境自由度的有限激发能来计算快速量子隧穿速率的耗散因子方法。我们还开发了一种称为动态范数法的方法，可用于定量估计大范围非绝热条件下的隧穿速率。对于裂变，我们以^<234>U为例，利用动力范数方法证明了由于核固有自由度的存在，自发裂变的寿命变得很短。我们还研究了从量子隧穿到热衰变的裂变机制，并预测了在原子核从超流体到正常状态相变的临界温度附近，配对帽能量的温度依赖性使裂变宽度显著减小。少

This project has been undertaken with the aim to develop theories and analyze data of macroscopic quantum tunneling in nuclear physics, centering on heavy-ion fusion reactions at energies near and below the Coulomb barrier and fission. Also, studies of related subjects such as elastic heavy-ion scattering, heavy-ion collisions induced by unstable nuclei, astrophysical nuclear reactions, nuclear structure in terms of relativistic mean field theory, medium energy heavy-ion collisions and microcluster physics have been undertaken. The main achievements are as follows : Concerning heavy-ion fusion reactions, we clarified the improtance of higher order coupling effects through the coupled-channels analyzes of the ^<64>Ni+92,96Zr and ^<16>O+^<112>Cd, ^<144>Sm fusion reactions, We also showed the important role playd by the anharmonicity in the vibrational coupling by describing the fusion of ^<16>O+^<112>Cd, ^<144>Sm with the interacting boson model. As an important consequence, our study sh … More ows that fusion data provide very useful information on anharmonic properties of nuclear vibrational modes of excitation and the sign of deformation of nuclei. Concerning the quantum tunneling in systems with many degrees of freedom, we have shown the importance of the mass renormalization in adiabatic quantum tunneling and developed a dissipation factor method to calculate the rate of fast quantum tunneling by taking the effects of a finite excitation energy of the environmental degrees of freedom. We also developed a method, called the dynamical norm method, which can be applied to quantitatively estimating the tunneling rate for a wide range of non-adiabaticity. As for fission, using ^<234>U as an example and using the dynamical norm method we have shown that the life time of spontaneous fission becomes very short due to the existence of nuclear intrinsic degrees of freedom. We also studied the transition of the fission mechanism from quantum tunneling to thermal decay, and have predicted that the fission width gets significantly reduced by the temperature dependence of the pairing cap energies near the critical temperature for the phase transition from superfluid to normal states of nuclei. Less