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

成形的超快激光脉冲可以有力地影响分子动力学，从而获得其他手段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通路的脉冲。然而，这究竟是如何实现的，往往是模糊的。本研究探讨如何从闭环控制中提取机械信息，从反馈信号的角度来处理这个问题。通过将图像纳入反馈回路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。反馈目标的微小变化与最佳脉冲特征的变化的相关性可以导致机械洞察。此外，控制的机制，可以随后探测与功率的速度图成像（VMI）或冷靶反冲离子动量谱（COLTRIMS）。实验将在堪萨斯州立大学进行，大部分实验前和实验后的工作将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本原理。为此，我们将构建，测试，并纳入反馈回路的多普勒自由动能释放光谱仪，能够解决特定的振动态的CO2+通过其分解成C++ O+。使用这种高分辨率的反馈，我们将寻求操纵振动人口，从而获得一个窗口的动态导致人口的瞬态CO2+。使用VMI作为反馈允许同时访问给定离子种类的角和动能释放（KER）信息。成形脉冲将用于控制乙炔二价阳离子异构化为CH 2 + + C+和乙烯阳离子异构化为CH 3 + + CH。这两个过程都可以用VMI和/或COLTRIMS探测。了解这些基准烃中异构化是如何控制的，可以为改进大分子中的控制提供基础。一个并行的次要方向将是实施新的反馈技术的自适应控制，如快速反演VMI频谱，以获得明确的KER数据。更广泛的影响：这项工作整合了各个层次的本科生，从实验设计到手稿准备。经验表明，这项活动既鼓励学生继续他们的科学训练，并提供了一个强大的背景研究生工作。该小组在促进妇女参与物理学方面有着良好的记录。科学上，对闭环相干控制中所涉及的分子动力学的更好理解将有利于几个应用，包括检测具有不良环境或国家安全特性的痕量材料，以及使用成形脉冲来创建用于量子计算的分子量子比特。对异构化动力学如何被操纵的更好理解可以进一步使分子开关和激光控制化学合成的发展成为可能。结果的传播将通过同行评审的出版物，会议演示，研讨会和专题讨论会，往往有学生。

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.