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Macroscopic Quantum Tunneling in Nuclear Reactions and Fission

核反应和裂变中的宏观量子隧道

基本信息

批准号：
06640368
负责人：
TAKIGAWA Noboru
金额：
$ 1.28万
依托单位：
Tohoki University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1994
资助国家：
日本
起止时间：
1994 至 1996
项目状态：
已结题

项目摘要

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

这个项目的目的是发展理论和分析核物理中宏观量子隧穿的数据，重点是库仑势垒附近和能量低于库仑势垒和裂变的重离子聚变反应。此外，还开展了相关学科的研究，如弹性重离子散射、不稳定核引起的重离子碰撞、天体物理核反应、相对论平均场理论下的核结构、中能重离子碰撞和微团簇物理。在重离子聚变反应方面，通过对^&lt；&gt；Ni+92，96Zr和^&lt；16&gt；O+^&lt；112&gt；Cd，^&lt；144&gt；Sm的耦合通道分析，阐明了高阶耦合效应的重要性，并用相互作用模型描述了^&lt；16&gt；O+^&lt；112&gt；Cd，^&lt；144&gt；Sm的聚变过程，说明了非谐性在振动耦合中的重要作用。作为一个重要的结果，我们的研究应该是…更多的聚变数据提供了关于核振动激发模式的非谐性质和核变形的迹象的非常有用的信息。对于多自由度系统中的量子隧穿，我们证明了质量重整化在绝热量子隧穿中的重要性，并提出了一种考虑环境自由度的有限激发能的影响来计算快量子隧穿速率的耗散因子法。我们还发展了一种称为动力范数方法的方法，该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^&lt；234&gt；U为例，用动力学范数方法证明，由于核固有自由度的存在，自发裂变的寿命变得很短。我们还研究了裂变机制从量子隧穿到热衰变的转变，并预言了核从超流到正常态相变的临界温度附近对帽能的温度依赖性使裂变宽度显著减小。较少