镝原子超精细结构能级的实验研究

Experimental researches concern cold dipolar interaction atoms have been a new project in cold atom physics. Dysprosium (Dy) atoms, chosen as ideal candidation experimental atoms due to its larger ground magnetic moments, are much easier in experimental production than that of ultracold molecules using Feshbach methods. The trapped Dy atoms in ground states are much stable in the state and massive in numbers so they have sufficient lifetime for following researches. In fact, Dy atoms consists of abundant open-shell electrons so they have much differences from alkaline or alkaline earth atoms in electronic configuration interactions and spectral terms of fine structure levels. This project aims at investigations and measurements of hyperfine structure levels of Dy atoms. We'll obtain some data about related levels, which are helpful to seek for appreciate methods of production of ultracold Dy atoms and also have contributions to comprehensive understanding of coupling methods of numerous open-shell electrons. We first produce two different frequency laser beams with AOMs, then scan the collimated hot Dy atom beam, the hyperfine structure level intervals can be obtained accurately with reduced nonlinear errors due to laser scan. At the same time, we can replace the hot Dy atom beam with an isolated isotope beam using laser deflection technology, which maybe bring conveniences in distinguishing between different isotope spectral lines.

对具有强偶极相互作用的冷原子体系的实验研究正成为冷原子研究中新的热点之一。镝（Dysprosium，Dy）原子由于其基态具有较大的磁偶极矩，因而可以作为理想的实验研究对象，超冷状态下的镝原子对比Feshbach方式产生的超冷分子在实验上实现方式更为简单，同时具有更高的稳定性和更多的粒子数。实验中，由于镝原子的外层电子排列的复杂性，某些激发态精细结构能级的耦合方式与碱（土）类原子大不相同。 因此本项目拟开展镝原子超精细结构能级的调查与测量工作，获取相关能级的各种常数，这些数据不仅可为镝原子激光冷却的方式提供能级参考，而且可以对开放壳层多电子的能级耦合方式加深理解。我们通过两束可调频率差的激光对准直后的热镝原子束进行扫描，从而获得原子跃迁的能级间隔，结合同位素分离技术可以将不同同位素的能级跃迁区分开来，从而减小原子束荧光谱中激光频率非线性变化对实验结果的不确定性贡献，并为能谱归类带来方便。

超冷磁性原子因具有大的磁偶极矩成为新的冷原子物理研究的焦点之一，而原子内部结构及同位素结构能级的研究在冷原子物理相关的实验研究中有非常基础性的作用。在激光冷却原子实验中，研究能级跃迁的封闭性、线宽和同位素位移间隔等对于高效地制备冷原子团有非常重要的指导意义，对于了解原子间相互碰撞过程也很有帮助。.我们建立了磁光阱中的单个原子的动力学模型和方程，给出光学饱和参数和磁场梯度等参数与最大捕获速度以及原子运动状态的关系，发现当激光饱和参数为2且失谐量为跃迁线宽一半时具有最大冷却效率。我们理论上详细研究了锂同位素和类锂的镁离子系统的同位素位移。基于MCDHF方法和GRASP2K程序分别讨论了质量效应（包括正常质量效应和特殊质量效应）和场效应对同位素位移的贡献。同时，我们研究了一种椭圆空心光纤中光束的轨道角动量的产生及其演化规律。这些工作将有助于镝原子的能级结构特性以及其激光冷却与囚禁实验研究。本项目截至今发表了两篇SCI文章和两篇国际会议报告。