| Co-Investigator(Kenkyū-buntansha) |
ABE Masanori Ishinomaki Senshu University, Faculty of Science and Engineering, Lecture, 理工学部, 講師 (50221049)
SINOZUKA Tsutomu Cyclotron Radioisotope Center Tohoku University, Research associate, 助手 (10134066)
ONO Akira Graduate School of Science Tohoki University, Research associate, 大学院・理学研究科, 助手 (20281959)
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| Research Abstract |
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
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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
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