RUI: Strong-Field Control of Polyatomic Molecules

普通观众摘要：超短激光脉冲具有的特性表明，它们可能被用来直接影响化学反应：激光施加的力可以与将分子结合在一起的电动力相媲美，在分子显著运动之前，脉冲可以被打开和关闭。因此，将定制的激光脉冲精确地应用于单个分子可能能够以目标、所需的方式对分子进行修饰。换句话说，激光可以被认为是一种驱动化学反应的新型试剂。这些基于激光的试剂的开发有朝一日可能使化学合成新材料和药物成为可能，这些材料和药物有助于公众的福祉。这一长期的目标已经取得了进展，但分子是复杂和动态的，这使得很难确定驱动特定过程的特定激光特性。这项工作探索了强激光场和分子之间相互作用的基本原理，以提高对设计适当的激光脉冲所需的理解。在本科生中做这项工作为进一步的科学教育提供了动力，因此有助于培养一支高技能的劳动力队伍。来自奥古斯塔纳大学的本科生利用堪萨斯州立大学J.R.麦克唐纳实验室的激光设备与那里的研究人员合作进行这项工作。技术观众摘要：这项工作使用成形的激光脉冲来启动分子动力学和复杂的检测方案来测量反应产物来探索多原子分子中的键重排。键重排以打乱、氢迁移和漫游等形式发生，包括任何化学反应中的几个步骤。通过将基于三维图像的快速反馈应用到键重排的闭环控制中，研究人员可以确定通过施加合适的激光场来控制化学反应中的这些关键步骤的程度。此外，研究人员还将提高飞行时间重合反馈的数据采集率，以实现闭环控制。在任何一种技术中，高度具体的反馈都会引导闭环搜索达到明确的目标。在使用多个激光脉冲的重排过程中，将电离步骤与对核波包的操作分开，使得对控制机制的检查更加直接。通过提高对强非微扰激光场的应用如何通过操纵宽带脉冲中频率分量的相对相位来影响过程的理解，该项目研究了一种广泛适用的相干控制方法。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

General audience abstract:Ultrashort laser pulses have properties that suggest they might be used to directly influence chemical reactions: the force exerted by the laser field can be comparable to the electric force that holds a molecule together, and the pulse can be turned on and off before the molecule will move significantly. Thus, the precise application of a customized laser pulse to an individual molecule might enable the modification of the molecule in a targeted, desired manner. Stated another way, the laser can be thought of as a new type of reagent that drives a chemical reaction. The development of these laser-based reagents could one day allow chemical synthesis of novel materials and medicines that contribute to the public well-being. Progress toward this long-standing goal has been made, but molecules are complex and dynamic, making it difficult to determine the specific laser characteristics to drive a particular process. This work probes the fundamentals of the interactions between strong laser fields and molecules to improve the understanding needed to design appropriate laser pulses. Doing this work with undergraduate students provides motivation for further scientific education and therefore helps develop a highly-skilled workforce. Undergraduate students from Augustana University carry out this work using the laser facilities of the J.R. Macdonald Laboratory at Kansas State University in collaboration with the researchers there.Technical audience abstract:This work probes bond rearrangement in polyatomic molecules using shaped laser pulses to initiate molecular dynamics and sophisticated detection schemes to measure the reaction products. Bond rearrangement, which occurs in forms such as scrambling, hydrogen migration, and roaming, encompasses several of the steps in any chemical reaction. By applying rapid three-dimensional image-based feedback to the closed-loop control of bond rearrangement, the investigators can determine how well these essential steps in a chemical reaction can be controlled by applying a suitable laser field. In addition, the researchers will increase the data acquisition rate of coincidence-time-of-flight feedback for closed-loop control. In either technique, the highly specific feedback guides the closed-loop search to a well-defined goal. Separating the ionization step from the manipulation of the nuclear wave packet during the rearrangement process using multiple laser pulses makes the examination of the control mechanism more direct. By improving the understanding of how the application of a strong, non-perturbative laser field can affect processes via manipulation of the relative phases of the frequency components in the broad bandwidth pulse, the project examines a widely applicable method of coherent control.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.