Theoretical Study of Resonance Phenomena in Electron-Capture Processes by Multiply-Charged Ions from Alkali-Metal Atoms.

在极低碰撞能量下，中性原子的多电荷离子捕获电子的过程中可能会出现共振现象，但目前尚未成功观察到。为了找出碰撞能量尽可能高时出现共振现象的碰撞系统，并明确共振现象的机理，我们用量子力学紧密耦合方法计算了He^<2+>、Be^<2+>、Be^<4+>、B^<3+>、B^<5+>、C^<2+>、C^<4+>、C^<6+>、N^<2+>、N^<3+>、N^<5+>、N^<7+>、Li^+、Li^<2+>、Li^<3+>离子与碱金属原子碰撞时的电子捕获横段。结果说明了这些碰撞体系的碰撞峰的能量和峰的宽度。研究了共振位置与目标原子、入射离子和电荷的关系。利用谱法得到了共振态的特征值和特征函数。采用多通道波包法研究了共振动力学，成功实现了共振现象的可视化。一般来说，目标原子极化率大、入射离子电荷高的体系，在碰撞能量高的情况下会出现共振。然而，我们必须注意势曲线的排斥力的出现。计算结果表明，在（He^<2+> + Li,Na）碰撞体系中，共振出现在最高碰撞能量（约0.3 eV）处。由于化学键形成的势阱比极化势阱深得多，我们只考虑最低的Σ_g和Σ_u态，计算了激光场中（H^+ + H）碰撞系统的截面。计算结果表明，在碰撞能量非常高的情况下（约2ev）会出现共振。

Resonance phenomena are expected to appear in electron capture processes by multiply-charged ions from neutral atoms at very low collision energies, but the observation has not yet been succeeded until now. In order to find out the collision systems in which the resonance phenomena appear at collision energy as high as possible and to make clear the mechanism for the resonance phenomena, we performed the calculations of the cross sections for electron capture with quantum mechanical close-coupling method in collisions of He^<2+>,Be^<2+>,Be^<4+>,B^<3+>,B^<5+>,C^<2+>,C^<4+>,C^<6+>,N^<2+>,N^<3+>,N^<5+>,N^<7+>,Li^+,Li^<2+>,Li^<3+> ions with alkali-metal atoms. As the results the collision energies at which peaks appear and the width of the peaks were elucidated for these collision systems. The dependence of the resonance-position on target atoms, incident ions, and charges were also investigated. Furthermore, the eigenvalues and eigenfunctions for resonance states were obtained by spectral method. The dynamics of resonance were investigated by multi-channel wave-packet method and the visualization of the resonance phenomena was succeeded.In general, the resonances appear at higher collision energy for the system in which the target atoms have large polarizability and incident ions have higher charge. However, we must call attention for the occurrence of the repulsion of potential curves. Our calculated results show that in the (He^<2+> + Li,Na) collision systems the resonances appear at most high collision energy (about 0.3 eV).Because the potential well due to bond-formation is much deep than that due to polarization, we calculated the cross sections for the (H^+ + H) collision system in laser field considering only the lowest Σ_g and Σ_u states. The calculated results show that resonances appear at very high collision energy (about 2 eV).