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

超快激光提供了足够短脉冲的“第一束光”，可以在相关的时间尺度上监测原子运动；低于百万分之一秒，就像定格摄影一样捕捉原子的动态。然而，传统光谱学的空间分辨率仅限于一个大病毒的大小。这大约是其精细程度的一万倍，无法观察到分子结构最精细的细节，甚至是其基本组成部分——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展，像LCLS（斯坦福大学）这样的大型，长达数公里的设施为我们提供了观察运动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“原子级”相机，其设计紧凑，可以放在标准办公桌大小的桌子上。他的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，可以直接访问原子空间和时间分辨率的结构动力学。特别关注强相关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在原子水平上理解新材料的结构-功能特性。我们还利用纳米流体技术研究了溶液中的有机金属配合物，以研究“d轨道”电子简并对核结构的影响，即Jahn Teller畸变。另一个备受关注的研究领域是超高速低温电子显微镜的发展。一项新技术将使我们能够在不需要结晶的情况下获得单粒子水平上生物分子的高分辨率（< 2 Å）结构。这条研究路线的长期目标涉及核糖体rna的原子分辨率结构研究。这条研究路线致力于在检查的原子水平上研究疾病状态的分子基础。这些研究对旨在预防疾病的药物设计至关重要。这些研究项目是高度跨学科的，是化学系、物理系量子物质组、先进材料连接中心材料工程组和滑铁卢生物化学和分子生物学研究所正在进行的努力的桥梁。仅仅在46年前，人们还认为过渡态、断键和成键事件是看不见的，而且速度快得无法测量。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，并由此能够对与物理、化学和生物学相关的动力学现象提供最基本的理解。我们的研究重点是这项使能技术，其基础科学和关键应用。

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.