Imaging chemical dynamics through laser-induced electron diffraction in the molecular-frame

通过分子框架中的激光诱导电子衍射对化学动力学进行成像

• 批准号: 281310165
• 负责人: Professor Dr. Jochen Küpper
• 金额: --
• 依托单位: Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie (MBI)
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 财政年份: 2015
• 资助国家: 德国
• 起止时间: 2014-12-31 至 2023-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/281310165?language=en
• 关键词: Imaging; chemical; dynamics; through; laser

Laser-induced electron diffraction (LIED) is an approach that allows for the atomic resolution imaging of structures and structural dynamics of molecules. Re-scattered electrons, emitted from strong-field ionization of molecules by intense mid-infrared pulses, are known to contain information on the exact (time-dependent) structures of simple molecules that can be extracted to record a "molecular movie" of chemical dynamics. However, the application of this technique to complex molecules and molecular dynamics requires strong control over the molecular sample, which needs to be spatially separated according to size, structural isomer, and quantum-state and to be strongly aligned and oriented.Here, we set out to advance methods to strongly control molecular samples of complex molecules and to use them to record precise structures of molecules and their dynamics using LIED. We will create beams of cold molecules using supersonic expansions and disperse these beams according to quantum-state, in order to create pure samples of individual states, species, or cluster sizes. Subsequently, the molecules will be strongly three-dimensionally aligned and oriented using moderately strong, tailored laser and dc electric fields. These samples, with all molecules looking identical in the laboratory frame, will be irradiated by an intense, mid-infrared, femtosecond pulse. The very strong electric field will ionize the molecules and accelerate the produced electrons. Eventually, the electron will re-scatter at the molecular ion, which was left behind. We will measure the momentum distribution of these electrons, in the molecular frame, and extract the electron diffraction pattern that will be inverted to yield a precise structure of the molecule. Adding an ultrashort UV pulse to start chemical dynamics will allow us to perform pump-probe experiments and to record snapshot of photo-initiated dynamics. In addition, we will develop rigorous theoretical models to invert the experimental data into atomic resolution molecular structures and dynamics movies.We will implement these investigations for complex polyatomic asymmetric-top molecules and molecular clusters, e.g., the prototypical peptide-chromophore indole and its water cluster, to investigate structural rearrangement reactions and so-called half collisions, in order to create clear pictures of these complex chemical-dynamics processes with high spatio-temporal resolution. The investigated systems range from the dissociation dynamics of the OCS molecule to the solvent-solute interaction in indole-water clusters. Our results will provide new insight into the molecular basis of chemistry and chemical reactions. Furthermore, the successful implementation of these methods will open avenues for applications of controlled molecules and strong-field physics in (structural) biology and (bio)chemistry.

激光诱导电子衍射是一种允许分子结构和结构动力学的原子分辨率成像的方法。通过强烈的中红外脉冲，从分子的强场电离中释放出的再散射电子，已知包含简单分子的精确（随时间变化的）结构信息，这些信息可以被提取出来，以记录化学动力学的“分子电影”。然而，将该技术应用于复杂分子和分子动力学，需要对分子样品进行强有力的控制，需要根据大小、结构异构体和量子态对分子样品进行空间分离，并进行强排列和定向。在这里，我们着手推进的方法，以严格控制复杂分子的分子样品，并使用它们来记录分子的精确结构和动态的使用。我们将使用超音速膨胀创造冷分子光束，并根据量子状态分散这些光束，以创造单个状态，物种或簇大小的纯样本。随后，分子将使用中等强度的、量身定制的激光和直流电场进行强烈的三维排列和定向。这些样品的所有分子在实验室的框架中看起来都是一样的，它们将被强烈的中红外飞秒脉冲照射。很强的电场会使分子电离，并加速产生的电子。最终，电子会重新散射到被留下的分子离子上。我们将测量这些电子在分子框架中的动量分布，并提取电子衍射图，该衍射图将被反转以产生分子的精确结构。添加超短紫外脉冲来启动化学动力学将使我们能够进行泵探测实验并记录光启动动力学的快照。此外，我们将建立严格的理论模型，将实验数据转化为原子分辨率的分子结构和动力学电影。我们将对复杂的多原子不对称顶部分子和分子簇（例如，典型的肽-发色团吲哚及其水簇）进行这些研究，以研究结构重排反应和所谓的半碰撞，以便以高时空分辨率创建这些复杂化学动力学过程的清晰图像。所研究的系统范围从OCS分子的解离动力学到吲哚-水团簇中溶剂-溶质相互作用。我们的研究结果将为化学和化学反应的分子基础提供新的见解。此外，这些方法的成功实施将为控制分子和强场物理在（结构）生物学和（生物）化学中的应用开辟道路。