碱金属-(类)碱土金属体系中可操控的碰撞动力学研究
文献类型：学位论文
| 作者 | 陈涛 |
| 学位类别 | 博士 |
| 答辩日期 | 2016 |
| 授予单位 | 中国科学院上海光学精密机械研究所 |
| 导师 | 王育竹 |
| 关键词 | 双原子分子结构 振动态转移 冷原子碰撞 Feshbach共振 冷分子 |
| 其他题名 | Controllable Collisions and Dynamics in Ultracold Alkali-Alkaline-Earth(-like) Mixtures |
| 中文摘要 | 利用外场调节超冷原子气体中的相互作用是目前被广泛采用的制备超冷分子的方法。以此为出发点，本论文重点研究碱金属-（类）碱土金属体系中可操控的冷碰撞散射问题，分两方面展开：一是双原子分子能级结构的理论分析工作，这是研究碰撞问题及分子态间转移动力学的基础；另一个是对碱金属-（类）碱土金属体系中的Feshbach 共振机制进行分析，进而探索制备冷分子的可能性。 首先，以RbSr 分子为例，我们详细讨论了碱金属-（类）碱土金属分子中的相互作用势能形式及振动态、转动态能级结构。通过相对论框架下的从头计算方法得到的势能曲线，我们计算了一系列振动态跃迁的Franck-Condon 系数，并据此选取合适的中间态来证明实现将分子转移到绝对基态的受激拉曼绝热转移通道的可行性，模拟的由弱束缚态分子到绝对基态的单边转移效率可达77%。 在计算相互作用势能的基础上，我们对碱金属原子与（类）碱土金属原子在外磁场下碰撞过程中的Feshbach 共振机制进行了探索。通过对基态碱金属-亚稳态（类）碱土金属体系的理论分析，我们发现确实存在由各向异性的相互作用势能诱发的宽的Feshbach共振。各向异性耦合主要来源于不同分波通道间的耦合以及不同精细结构能级通道的耦合，且这两者均与亚稳态（类）碱土金属原子的轨道角动量自由度相关。然而，这些较宽的共振也伴随着很大的非弹性碰撞损失率（在10?10 cm3s?1 量级），即磁场下亚稳态原子会弛豫到能级较低的精细结构能级或塞曼子能级上，这将极大地限制利用Feshbach共振在该体系中实现分子的制备，特别是将分子转移到基态将是一个特别复杂且难以精确操控的过程。 最后简要介绍了RbYb 光缔合实验中的两个设计工作，即能同时减速两种原子的塞曼减速器和磁光阱磁场线圈的制作与测量。 总之，本文围绕利用外场下的原子碰撞实现分子制备这一主题，系统地对碱金属-（类）碱土金属这一实验上极具挑战的分子体系进行了分析，包括计算相互作用势能形式的从头计算方法，到对分子振动态转移过程的模拟，以及对利用Feshbach 共振来制备该体系分子的可能性探索，这些结论对未来该体系的理论及实验研究均具有重要的启发和指导意义。 |
| 英文摘要 | Tuning the interatomic interactions with external fields is currently the most widely used method to create ultracold molecule. For this point, the dissertation focuses investigations on cold collisions in alkali-alkaline-earth(-like) system, mainly in two aspects: one is theoretical analyses of the diatomic molecular structures, which is required in research on collision problem and transferring dynamics between molecular states; another is analysis on the Feshbach mechanism in alkali-alkaline-earth(-like) system, and further exploring the possibility of forming ultracold molecule. First, we present the calculation details on the interatomic potentials and rovibational level structures of RbSr molecule. Accroding to the Franck-Condon factors for series of vibrational transitions based on the potential energy curves yielded with relativistic ab initio quantum chemistry methods, a proper intermediate state is chosen to demonstrate the feasibility of transferring molecule into the absolute ground state, and the simulated one-way transfer efficiency from weakly-bound state to absolute ground state can reach 77%. With detailed knowledge of the atomic interaction potentials, we make an exploration of the magnetic Feshbach resonance in alkali-alkaline-earth(-like) system. Theoretical scattering calculations on collisions between ground-state alkali-metal atom and metastable-state alkaline-earth(-like) atom lead to a conclusion that, unlike the role of the electronic spin degree of freedom in collisions of two alkali-metal atoms, the orbital degrees of freedom from p electron of the metastable atoms, which induce not only mixings between different partial waves but also couplings between channels in different fine structure manifolds, introduce the anisotropic interactions for producing broad enough Feshbach resonances. However, the resonances also suffer from large inelastic rate at the magnitude of 10?10 cm3s?1 to lower-lying fine structure states or Zeeman sublevels, which will be an obstacle for associating ultracold polar molecules with both electron spin and electric dipole momentum, especially the process of transferring the molecule to ground state will be complex and indisciplinable. Finally we make a brief introduction of the design, construction and test of the dual-species Zeeman slower and the water-cooled magnetic coils for the magneto optical trap in our RbYb photoassociation experiments. In conclusion, the dissertation intends to explore some new points on molecular formation via cold collisions controlled by external field. The results and conclusions on the specially challenging alkali-alkaline-earth(-like) system, including the ab initio methods for calculating interaction potentials, the simulations of the vibrational state transferring procedure, and the exploration on the possibility of producing ultracold molecule via magnetic Feshbach resonance, provide promising inspirations and directions for future theoretical and experimental studies on such systems. |
| 语种 | 中文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/15989]  |
| 专题 | 上海光学精密机械研究所_学位论文 |
| 推荐引用方式 GB/T 7714 | 陈涛. 碱金属-(类)碱土金属体系中可操控的碰撞动力学研究[D]. 中国科学院上海光学精密机械研究所. 2016. |
入库方式： OAI收割
来源：上海光学精密机械研究所
浏览0
下载0
收藏0
其他版本
除非特别说明，本系统中所有内容都受版权保护，并保留所有权利。