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

这项研究计划将制作“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。这项研究的目标是确定在大分子中发生光诱导转变所需的时间。这一点很重要，因为光诱导的过程在我们的环境中持续发生，例如来自地球大气层、植物叶子和人类皮肤上的阳光。这个团队将使用强大的桌面激光脉冲来录制“分子电影”。一个脉冲将被用来引发分子价电子轨道的电离，然后第二个脉冲和离子探测系统将被用来捕捉转变的时间演化。将要研究的分子，包括乙醇和面体内富勒烯，与工业相关，可以作为该团队开发的测量方案的试件。这个项目将制作的分子电影非常重要，因为它们将揭示驱动与这些分子发生特定反应的物理和化学过程。接受这个项目培训的学生和博士后将学习他们将在未来的学术界和工业界工作中使用的技能。本研究将集中研究长波多光子电离中醇的时间分辨光致异构化和内面体富勒烯(M3n@C80)的时间演化和隧穿机制。后一项实验的目标是了解激发超原子分子轨道(SAMO)态在这两个不同能量区域中的作用。这些实验将使用桌面激光泵浦-探测技术进行，并将使用被称为冷靶反冲离子动量谱(COLTRIMS)系统的电子-离子-离子符合监测器来探测产生的带电碎片。因此，通过符合离子动量成像将揭示潜在的动力学。这个团队对先进科学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来实现的，这将使双色泵浦-探测实验成为可能，并将突破目前基本的飞秒时间分辨大分子动力学研究的极限。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不一致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.