Molecular Resonances and Nuclear Structure in Heavier Systems

本课题旨在阐明^<24>Mg + ^<24>Mg和^<28>Si + ^<28>Si等重离子散射的共振机制。1. 我们假设弹丸核具有轴对称变形。在新的分子模型中，双核体系的运动被描述为旋转的分子框架和与此框架相关的集体运动。我们量化了系统的哈密顿量，并将其项分为旋转和振动项、模模耦合项和科里奥利项。利用核-核相互作用的折叠模型势，发现长形变形核的稳定构型为极-极构型，扁形变形核的稳定构型为边-边构型。2. 对^<24>Mg + ^<24>Mg体系进行了研究，阐明了极-极结构的正常振动模式如下：由于恢复力较弱，两极之间的扭转模式具有类似旋转的特征。对于相对运动和偏离分子轴的两个极向这三个内部变量，我们可以通过恢复势的二次展开来求解运动方程。发现这些内部旋转和振动模式的激发能几乎是简并的。3. 将这些解析解作为基解，对角化了扭转相互作用（模-模耦合项）。得到了正模谱，其K = 0能级密度与实验结果吻合较好。4. 我们研究了衰变宽度。结果表明，在45.7MeV共振状态下，（2^+,0^+），（2^+,2^+）通道有较强的衰减。此外，在激发函数中还观察到6^+等高自旋非弹性通道的强衰减。我们发现，在高激发态下，振幅在（6^+,0^+）和（6^+,2^+）通道中被极大地压缩。

The aim of the present research project is to clarify the resonance mechanisms in heavy-ion scattering such as ^<24>Mg + ^<24>Mg and ^<28>Si + ^<28>Si , etc.. 1. We assume axialsymmetric deformation for projectile nucleus. In the new molecular model, the motions of the di-nuclear system are described in terms of the rotating molecular frame and the collective motions referred to this frame. We have quantized the Hamiltonian of the system, and have classified its terms into rotational and vibrational ones, mode-mode coupling ones and Coriolis ones. With folding-model potential for the nucleus-nucleus interaction, the stable configuration of the system is found to be the pole-pole one for prolate deformed nuclei, and the edge-edge one for oblate deformed nuclei. 2. The ^<24>Mg + ^<24>Mg system has been studied and normal modes of vibration in the pole- pole configuration are clarified as follows. The twisting mode between two poles has rotation-like feature due to the weak restoring force. Concerning to the other three internal variables, i.e., the relative motion and two pole-directions shifted from the molecular axis, we can solve the equation of motion by means of quadratic expansion of the restoring potential. Excitation energies of these internal rotation and vibrational modes are found to be almost degenerate. 3. By using these analytical solutions as basis ones, we have diagonalized twisting interaction (mode-mode coupling terms). We have obtained normal mode spectrum, K = 0 level density of which appears to be in good agreement with experiment. 4. We have investigated decay widths. The results show strong decays to the (2^+, 0^+), (2^+, 2^+) channels concerning to the state for the 45.7MeV resonance. Furthermore strong decays to high-spin inelastic channels such as 6^+ are observed in the excitation functions. We have found that the amplitudes are greatly condensed in the (6^+, 0^+) and (6^+, 2^+) channels in the highly-excited states.