Theoretical study of the scattering of unstable nuclei and the synthesis of superheavy elements

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This research project aimed at exploring characteristics of heavy-ion collisions induced by unstable nuclei, especially by halo nuclei, and at finding a new way to synthesize superheavy elements. The structure of unstable nuclei and quantum tunneling in multi-dimensional systems were also studied as closely related subjects. The main achievements are as follows. 1. We studied the effect of projectile berak-up on the heavy-ion fusion reactions induced by a halo nucleus, and showed that one can still expect a larger fusion cross section for a halo nucleus than for the other isotopes at energies below the Coulomb barrier, though the projectile break-up moderates the large enhancement of the fusion cross section suggested in one of our previous papers for the collisions of a halo nucleus. 2. We showed that the differential cross section of the elastic scattering in medium energy heavy-ion collisions has a steeper fall off at angles where the so called far-side component dominates if a halo nucleus is used as the projectile. 3. We studied multi-nucleon transfer neactions in deep inelastic heavy-ion collisions based on a transport theory, and found that much larger number of neutrons are exchanged than protons if a halo nucleus is used as the projectile. 4. We showed that the tranverse momentum distribution of the projectile fragments in medium energy heavy-ion collisions gets narrower by reflectiong the reaction mechanism. 5. We studied the effects of environments on the tunneling rate of a macroscoic variable, and showed the importahce of a mass renormalization in the cases, where the environments have slightly shorter time scale than that of the tunneling process. Also, we developed a method, the method of dynamical norm factor, to treat non adiabatic effects in macroscopic quantum tunneling, and demonstrated its numerical accuracy by a few model calculations. Using this method, we analyzed the fission of ^<234>U, and showed that the coupling to a nuclear intrins