Femtosecond electron sources for atomically-resolved dynamics and ultrafast high-resolution imaging

超快激光器提供了“第一束光”，脉冲足够短，可以在相关的时间尺度上监测原子的运动;低于百万分之一秒，可以像定格摄影一样捕捉飞行中的原子。然而，传统光谱学的空间分辨率仅限于大病毒的大小。这是大约一万倍太粗糙观察分子结构在其最精细的细节，下降到其基本的积木-原子。在过去的20年里，超快结构敏感相机的发展取得了巨大的进步，大型的，长达数公里的设施，如LCLS（斯坦福大学），为我们提供了观察运动中的原子所需的时间和空间分辨率。Germán Sciaini领导着滑铁卢大学的一个小组，该小组开发了这种紧凑设计的“原子级”相机，可以放在标准办公桌大小的桌子上。他的照相机是基于使用超短和明亮的电子爆发，可以应用于广泛的结构问题。我们的团队开发了自制的超快电子衍射装置，可以直接访问具有原子空间和时间分辨率的结构动力学。特别关注强关联的过渡金属氧化物和有机金属材料的研究。电子-电子、电子-声子和声子-声子相互作用的动力学研究使我们能够从原子水平上理解新材料的结构-功能特性。我们还实施nanofluidics的研究溶液中的有机金属配合物，以调查的影响，“d轨道”的电子简并对核结构，即Jahn Teller失真。另一个非常感兴趣的研究领域是超快冷冻电子显微镜的发展。一种新技术，将使我们能够在单粒子水平上获得生物分子的高分辨率（<2 μ m）结构，而无需结晶。这条研究线的长期目标包括原子分辨率的核糖体RNA结构研究。这条研究线致力于在原子水平上研究疾病状态的分子基础。这些研究对于旨在预防疾病的药物设计至关重要。这些研究项目是高度多学科的，并在化学系，物理系量子物质组，先进材料加入中心的材料工程组以及滑铁卢生物化学和分子生物学研究所正在进行的努力中架起了桥梁。仅仅在46年前，过渡态、键断裂和键形成事件还被认为是不可见的，而且速度不可估量。如今，我们已经达到了观察运动中的原子所需的空间和时间分辨率，并且能够提供与物理，化学和生物学相关的动力学现象的最基本的理解。我们的研究重点是这种使能技术，其基础科学及其关键应用。

Ultrafast lasers provided the “first light” in sufficiently short pulses to monitor atomic motion on the relevant timescales; below a millionth of a millionth of a second, to literally catch atoms on the fly as in stop-motion photography. However, the spatial resolution in conventional optical spectroscopy is limited to about the size of a big virus. This is about ten thousand times too coarse to observe the molecular structure at its finest detail, down to its fundamental building blocks – atoms. The progress in the development of ultrafast structure-sensitive cameras over the last 20 years has been tremendous, with large scale, kilometers long facilities such as LCLS (Stanford) built to provide us with the temporal and spatial resolutions required to observe atoms in motion. Germán Sciaini heads a group at the University of Waterloo that develops such “atomic-level” cameras in a compact design that fits on a table with the size of a standard office desk. His cameras are based on the use of ultra-short and bright electron bursts which can be applied to a wide range of structural problems. Our group develops home-built ultrafast electron diffraction setups which provide direct access to structural dynamics with atomic spatial and temporal resolutions. Special attention is paid to the study of strongly correlated transition metal oxides and organometallic materials. Dynamical studies of electron-electron, electron-phonon, and phonon-phonon interactions allow us to achieve an atomic-level understanding of structure-functional properties of novel materials. We also implement nanofluidics for the study of organometallic complexes in solution to investigate the effect of "d orbital" electronic degeneracy on the nuclear structure, i.e. Jahn Teller distortion. Another research area of great interest is the development of ultrafast cryo-electron microscopy. A new technique that will allow us to gain access to high-resolution (< 2 Å) structures of biomolecules at the single particle level without the need of crystallization. The long term goal of this research line involves structural studies of ribosomal-RNAs with atomic resolution. This research line is devoted to the investigation of the molecular basis of disease states at the atomic level of inspection. These studies are crucial for drug design aimed at the prevention of illness. These research programs are highly multidisciplinary and bridge ongoing efforts in the Department of Chemistry, the Quantum Matter Group in the Department of Physics, the Materials Engineering Group in Centre for Advanced Materials Joining, and the Institute of Biochemistry and Molecular Biology of Waterloo. Only 46 years ago, transition states, bond breaking and bond formation events were thought to be invisible and immeasurably fast. Nowadays, we have reached the spatial and temporal resolutions required to observe atoms in motion and, with that, been able to provide the most fundamental understanding of dynamical phenomena relevant to physics, chemistry, and biology. Our research is focused on this enabling technology, its fundamental science and its critical applications.