Visualizing Molecular Dynamics in Large Molecules using Intense, femtosecond, Pump-Probe Laser Pulses

这个研究项目将制作“分子电影”，用于研究激光在分子中诱导的基本物理和化学过程。这项研究的目的是确定在大分子中发生光诱导转化所需的时间。这一点很重要，因为光诱导过程在我们的环境中不断发生，例如，阳光照射在地球大气、植物叶子和人类皮肤上。这个团队将使用强大的桌面激光脉冲来记录“分子电影”。一个脉冲将用于启动分子价电子轨道的电离，然后第二个脉冲和离子检测系统将用于捕获转换的时间演化。将被研究的分子，包括乙醇和内嵌富勒烯，与工业相关，可以作为该团队开发的测量方案的测试品。这个项目将要制作的分子电影很重要，因为它们将揭示驱动这些分子特定反应的物理和化学过程。在这个项目中接受培训的学生和博士后学习的技能将用于未来在学术界和工业界的工作。本研究项目将重点研究长波长（IR）多光子电离和隧道机制下醇的时间分辨光诱导异构化和内嵌富勒烯（M3N@C80）的时间演化。后一个实验的目标是了解在这两种不同的能量状态下，受激超原子分子轨道（SAMO）的作用。实验将使用台式激光泵浦探测技术进行，产生的带电碎片将使用称为冷目标反冲离子动量光谱（COLTRIMS）系统的电子-离子-离子一致性监测器进行检测。因此，潜在的动力学将通过同步离子动量成像来揭示。这个团队对科学进步的贡献源于他们在飞秒尺度上实时探测物理和化学过程的先进方法。这是通过使用带有双光学参数放大器的强飞秒台式激光器实现的，这将使双色泵浦探针实验成为可能，并将推动飞秒时间分辨大分子动力学研究的基本限制。这项工作将与理论家合作完成，这将使该团队能够定量地了解物理过程的复杂性，并将在实验和理论之间存在分歧的情况下验证或推进计算/建模。

This research program will make "molecular movies" that will be used to study fundamental physical and chemical processes induced in molecules by laser light. The goal of this investigation is to determine the time it takes for light-induced transformations to occur in large molecules. This is important because light-induced processes occur continuously in our environment, for example from sunlight shining on earth's atmosphere, plant leaves, and human skin. This team will record "molecular movies" by using strong table-top laser pulses. One pulse will be used to initiate the ionization of the molecular valence electrons orbitals, and then a second pulse and an ion detection system will be used to capture the time-evolution of the transformation. The molecules that will be studied, including ethanol and endohedral fullerenes, are relevant for industries and can serve as test-pieces for the measurement protocols developed by this team. The molecular movies that this project will produce are important because they will reveal physical and chemical processes that drive specific reactions with these molecules. Students and postdocs that get trained on this project learn skills that they will use for future jobs in academia and industry. This research program will focus on investigating the time-resolved photo-induced isomerization of alcohol and the time evolution of endohedral fullerenes (M3N@C80) in the long-wavelength (IR) multiphoton ionization and the tunneling regimes. The goal for the latter experiment is to understand the role of excited super atomic molecular orbital (SAMO) states in these two different energy regimes. The experiments will be carried out using table-top laser pump-probe technique and the resulting charged fragments will be detected using an electron-ion-ion coincidence monitor known as a Cold-Target Recoil Ion Momentum Spectroscopy (COLTRIMS) system. The underlying dynamics will thus be revealed by coincident ion-momentum imaging. This team's contribution to advance science stems from their advanced approach to probe, in real time, and at the femtosecond scale, physical and chemical processes. This is achieved by using intense femtosecond table-top laser with twin optical parametric amplifiers which will enable 2-color pump-probe experiments and will push the current limit of fundamental femtosecond time-resolved large molecular dynamics investigations. This work will be done in partnership with theorists, which will allow this team to understand quantitatively the complexity of the physical processes and which will validate or push forward the calculations/modeling in cases of disagreements between experiment and theory.