RUI: Using Imaging Methods to Expose the Molecular Dynamics Arising from Ultrafast Adaptive Control

RUI：使用成像方法揭示超快自适应控制产生的分子动力学

• 批准号: 0969687
• 负责人: Eric Wells
• 金额: $ 13.97万
• 依托单位: Augustana University Association
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-08-01 至 2014-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0969687&HistoricalAwards=false
• 关键词: RUI; Using; Imaging; Methods; Expose

Shaped ultrafast laser pulses can powerfully influence molecular dynamics, thus allowing access to outcomes not typically available by other means. The complexities of the field-molecule interaction generally make an a priori determination of the required field characteristics impossible, and so adaptive feedback algorithms are often employed to identify the optimal pulse. This technique efficiently selects pulses that enhance the desired pathway. Exactly how this is accomplished, however, is often obscure. This research examines ways to extract mechanistic information from closed-loop control by approaching this problem from the perspective of the feedback signal. By incorporating images into the feedback loop or using vibrational-state specific feedback we can query the search algorithm in very specific ways. Correlation of small changes in the feedback target with changes in the optimal pulse traits can lead to mechanistic insight. Furthermore, the mechanisms underlying the control can be subsequently probed with the power of velocity map imaging (VMI) or cold-target recoil-ion momentum spectroscopy (COLTRIMS). Experiments will be conducted at Kansas State University with much of the pre- and post-experiment work carried out at Augustana College. The primary aim of these experiments is to uncover the fundamentals of the molecular dynamics in these interactions. To this end, we will construct, test, and incorporate into the feedback loop a Doppler-free kinetic energy release spectrometer that is capable of resolving specific vibrational states of CO2+ through its dissociation into C+ + O+. Using this high resolution feedback, we will seek to manipulate the vibrational population and thereby gain a window into the dynamics leading to population of the transient CO2+. Using VMI as feedback allows simultaneous access to angular and kinetic energy release (KER) information for a given ion species. Shaped pulses will be used to control the isomerization of the acetylene di-cation into CH2 + + C+ and the ethylene cation into CH3 + + CH. Both of these processes can be probed with VMI and/or COLTRIMS. Understanding how isomerization is controlled in these benchmark hydrocarbons can provide a foundation for improved control in larger molecules. A concurrent secondary direction will be the implementation of new feedback techniques for adaptive control, such as the rapid inversion of VMI spectra to obtain unambiguous KER data. Broader Impacts: This work integrates undergraduates at all levels, from experiment design to manuscript preparation. Experience has shown that this activity both encourages students to continue their science training and provides a strong background for graduate work. The group has a good record of promoting the participation of women in physics. Scientifically, improved understanding of the molecular dynamics involved in closed-loop coherent control will benefit several applications, including detection of trace amounts of materials with undesirable environmental or national security traits and the use of shaped pulses for the creation of molecular qubits for quantum computing. Improved understanding of how isomerization dynamics can be manipulated could further enable the development of molecular switches and laser-controlled chemical synthesis. Dissemination of results will occur through peer-reviewed publications, conference presentations, and seminars and symposiums that often feature students.

成形超快激光脉冲可以强烈影响分子动力学，从而获得其他方法通常无法获得的结果。场-分子相互作用的复杂性通常使得不可能先验地确定所需的场特性，因此通常采用自适应反馈算法来识别最佳脉冲。该技术有效地选择增强所需途径的脉冲。然而，具体是如何实现这一点的却常常是模糊的。本研究从反馈信号的角度解决这个问题，探讨从闭环控制中提取机械信息的方法。通过将图像合并到反馈环中或使用振动状态特定反馈，我们可以以非常特定的方式查询搜索算法。将反馈目标的微小变化与最佳脉冲特征的变化相关联可以产生机制洞察。此外，随后可以利用速度图成像（VMI）或冷目标反冲离子动量谱（COLTRIMS）的力量来探测控制背后的机制。实验将在堪萨斯州立大学进行，实验前和实验后的大部分工作在奥古斯塔纳学院进行。这些实验的主要目的是揭示这些相互作用中分子动力学的基础知识。为此，我们将构建、测试并将其纳入反馈回路中的无多普勒动能释放光谱仪，该光谱仪能够通过解离成 C++ O+ 来解析 CO2+ 的特定振动状态。利用这种高分辨率反馈，我们将寻求操纵振动群体，从而获得一个了解导致瞬态 CO2+ 群体的动力学的窗口。使用 VMI 作为反馈可以同时访问给定离子种类的角能和动能释放 (KER) 信息。整形脉冲将用于控制乙炔二阳离子异构化为CH2++C+以及乙烯阳离子异构化为CH3++CH。这两个过程都可以使用 VMI 和/或 COLTRIMS 进行探测。了解如何控制这些基准碳氢化合物的异构化可以为改进对较大分子的控制奠定基础。并行的次要方向将是实施用于自适应控制的新反馈技术，例如快速反演 VMI 频谱以获得明确的 KER 数据。更广泛的影响：这项工作整合了从实验设计到手稿准备的各个级别的本科生。经验表明，这项活动既鼓励学生继续进行科学训练，又为研究生工作提供了坚实的背景。该组织在促进女性参与物理学方面有着良好的记录。从科学角度来看，提高对闭环相干控制涉及的分子动力学的理解将有利于多种应用，包括检测具有不良环境或国家安全特性的痕量材料，以及使用整形脉冲创建用于量子计算的分子量子位。更好地了解如何操纵异构化动力学可以进一步促进分子开关和激光控制化学合成的发展。结果的传播将通过同行评审的出版物、会议演讲以及通常由学生参加的研讨会和座谈会进行。