Molecular Resonances and Nuclear Structure in Heavier Systems

本研究项目的目的是阐明重离子散射中的共振机制，如^&lt；24&gt；mg+^&lt；24&gt；mg和^&lt；28&gt；Si+^&lt；28&gt；Si等。1.假定弹核为轴对称形变。在新的分子模型中，双核系统的运动被描述为旋转的分子框架和参考该框架的集体运动。我们量子化了系统的哈密顿量，并将其分为转动项和振动项、模模耦合项和科里奥利项。在核-核相互作用的折叠模型势下，系统的稳定构型对于长形变核是极-极构型，对于扁平形变核是边-边构型。2.对^&lt；24&gt；mg+24&gt；mg体系进行了研究，明确了杆-杆组态的简正振型。由于恢复力较弱，两极间的扭转模式具有类旋转性。对于另外三个内变量，即相对运动和两个极点方向偏离分子轴，我们可以通过恢复势的二次展开来求解运动方程。发现这些内转动和振动模式的激发能几乎是简并的。3.以这些解析解为基础，我们得到了对角化的扭转相互作用(模模耦合项)。我们得到了简正模谱，K=0能级密度与实验符合得很好。4.我们研究了衰变宽度。结果表明，对于45.7 MeV的共振，(2^+，0^+)，(2^+，2^+)通道有较强的衰变。此外，在激发函数中观察到了对高自旋非弹性通道的强衰变，如6^+。我们发现，在高激发态下，(6^+，0^+)和(6^+，2^+)通道中的振幅发生了极大的凝聚。

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.