High-Resolution Spectroscopy of Heteronuclear Alkali Molecules: Structure and Dynamics

该项目是一个联合实验和理论研究计划，解决高分辨率分子光谱和碰撞动力学领域的重要问题。光谱研究包括对nac和其他异核碱分子三重态的反振动能级的测量，以及这些能级的精细和超精细结构的研究。目标是绘制势能曲线，研究状态之间的自旋轨道和非绝热耦合，并利用能级模式，特别是精细和超精细结构的逐级变化，来推断基本的分子相互作用。通过与理论模型的比较，我们已经确定了许多重要的动力学效应。特别是NaK分子，它表现出了幸运的特性组合，使其成为研究分子超精细结构的有趣“实验室”。例如，我们最近的观察表明，不同的电子状态（甚至同一状态内不同的反振动能级）表现出几种不同的角动量耦合方案，包括纯和中间情况。这些精细和超精细结构的水平变化包含了电子波函数作为核间分离函数的细微变化的信息。已经发展了实验和理论技术来提取这些信息。进一步的高分辨率研究将用于探测更接近解离极限的振动水平；在这个范围内的数据将提供关于远程相互作用的信息，并将导致更好地理解电子波函数在系统从分离原子过渡到分子状态时的微妙变化。我们还将研究NaCs，它对冷却和捕获以及提出的量子计算方案感兴趣。该分子中较大的自旋轨道相互作用，导致强扰动和避免交叉，为实验和理论提供了有趣的新挑战。我们的项目还研究了各种碰撞过程，包括激发转移，分子取向转移，以及改变原子超精细水平或分子振动水平的碰撞速度变化。这些研究将为原子和分子碰撞理论提供严格的检验。更广泛的影响是异质核分子如NaK和NaCs的光谱研究引起了广泛的兴趣。具有永久偶极矩的超冷异核碱双原子原则上可以在光学晶格中定向，这表明在量子计算方案中的应用。Na-Cs和Rb-Cs混合物被用于混合种原子陷阱中，分子电子态的知识对于理解光缔合光谱具有特别的意义。提高对原子和分子碰撞动力学的理解将导致在从高温等离子体到超冷状态的广泛环境建模方面取得进展。这项工作将有助于许多学生的教育。三到四名研究生将根据本提案中描述的项目撰写博士论文。夏季期间，至少有六名本科生将通过利哈伊大学的REU项目与合作项目负责人一起工作。在过去的25年里，有60名本科生与合作pi一起进行了各种研究项目。这些学生中有一半以上是女性，其中6人属于代表性不足的少数群体；这种模式可能会继续下去。合作项目将继续派遣研究生和本科生参加APS DAMOP和其他国家会议。

This project is a joint experimental and theoretical research program addressing important questions in the areas of high-resolution molecular spectroscopy and collision dynamics. The spectroscopic studies involve measurements of the ro-vibrational energy levels of triplet states of NaCs, and other heteronuclear alkali molecules, and the investigation of fine and hyperfine structure of these levels. The goal is to map out potential energy curves, study spin-orbit and nonadiabatic coupling between states, and to use the pattern of energy levels, particularly the level-by-level changes in the fine and hyperfine structure, to infer fundamental molecular interactions. By comparing data with theoretical models, we have already identified many important dynamical effects. The NaK molecule, in particular, exhibits a fortunate combination of properties that make it an intriguing "laboratory" for the study of molecular hyperfine structure. For example, our recent observations have revealed that different electronic states (and even different ro-vibrational levels within the same state) exhibit several different angular momentum coupling schemes, including both pure and intermediate cases. These level-to-level variations in the fine and hyperfine structure contain information about subtle changes in the electronic wave functions as a function of internuclear separation. Experimental and theoretical techniques have been developed to extract this information. Further high-resolution studies will be done to probe vibrational levels closer to the dissociation limit; data in this range will provide information about long range interactions and will lead to a better understanding of the delicate changes in the electronic wave function as the system makes the transition from the separated atom to the molecular regime. We will also study NaCs, which is of interest for cooling and trapping and for proposed quantum computing schemes. The large spin-orbit interactions in this molecule, leading to strong perturbations and avoided crossings, provide interesting new challenges for both experiment and theory. Our program also studies a variety of collision processes including excitation transfer, transfer of molecular orientation, and velocity changes in collisions that change atomic hyperfine level or molecular rovibrational level. Such studies will provide stringent tests of atomic and molecular collision theory. Broader impacts are that spectroscopic studies of heteronuclear molecules such as NaK and NaCs are of wide interest. Ultracold heteronuclear alkali diatomics, which have permanent dipole moments, can in principle be oriented in an optical lattice, suggesting applications in quantum computing schemes. Na-Cs and Rb-Cs mixtures are being used in mixed species atom traps, and knowledge of the molecular electronic states is of particular interest for understanding photoassociation spectra. Improved understanding of atomic and molecular collision dynamics will lead to progress in modeling a wide range of environments, from high temperature plasmas to the ultracold regime. The work will contribute to the education of many students. Three or four graduate students will write Ph.D. dissertations based on the projects described in this proposal. At least six undergraduate students will work with the co-PIs during the summers through Lehigh University's REU program. Over the past 25 years, 60 undergraduate students have worked with the co-PIs on various research projects. More than half of these students are female and six belong to underrepresented minority groups; that pattern is likely to continue. The co-PIs will continue to send both graduate and undergraduate students to the APS DAMOP and other national meetings.