The Center for Chemistry at the Space-Time Limit (CaSTL)

时空极限化学中心(CaSTL)专注于发展可用于观察和记录分子在原子和化学键水平上的运动的新科学。这套新工具，统称为化学显微镜，将通过可视化分子内原子的运动来揭示新的见解，因为它们振动、形成新的键或催化化学反应。调查人员正在特别关注太阳能转化为化学形式能源的过程细节，希望实时捕捉到这一关键的能源转换事件。这项工作正在产生更广泛的影响，因为开发了在非常精细的范围内将化学事件可视化的新技术，并通过在各种公共媒体上传播其结果。这项工作正在通过发明新的科学工具来推动创新，这些工具正在走向商业开发。除了直接为参与中心研究的学生的教育发展做出贡献外，CASTL还组织和参与各种正式和非正式的科学教育活动，面向不同教育背景的受众。例子包括更广泛的化学界的暑期学校，针对高中生的加州州立数学与科学暑期学校(COSMOS)，以及各种非正式的科学教育活动，如男孩和女孩俱乐部的课外计划。在这一资助期间，CaSTL将继续开发全光学版本的工作化学显微镜，以及将光学与扫描探针显微镜相结合的版本，以及在飞秒-埃时空尺度上对分子运动和变化的最终观察。该小组正致力于将该工具应用于特定的化学问题，特别是等离子体增强的光催化。集体电子的激发，热电子的形成，它们在界面上的热化和散射，电子或空穴注入催化分子中心，以及随后的键断裂和形成，都是在时空中捕获的目标。通过对催化金属团簇和异质结构的时间分辨光电子发射显微镜(tr-PEEM)和双光子光电子能谱(tr-2PP)，他们正致力于全面表征等离子体激发时金属一侧启动的时空动力学。利用时空分辨的表面增强非线性相干光谱技术，实现了光催化分子表面转变的完整时间过程。正在使用理论研究来指导这一独特工具集的功能的开发和改进。作为该中心工作的结果，从催化中涉及的小分子到设备的工程化中尺度结构，人们设想对光物理和化学有一个完整的理解。

The Center for Chemistry at the Space-Time Limit (CaSTL) focuses on the development of novel science that can be used to observe and record motions of molecules at the atomic and chemical bond level. This set of new tools, collectively known as the chemiscope, will reveal new insights by visualizing the motions of atoms within molecules as they vibrate, form new bonds or catalyze chemical reactions. The investigators are paying special attention to the details of the process by which solar energy is converted to chemical forms of energy, hoping to catch this crucial energy conversion event in the act, in real time. The work is having a broader impact through the development of new technologies for visualizing chemical events on a very fine scale, and also through the dissemination of their results in a variety of public media. The work is furthering innovation through the invention of new scientific tools that are being moved toward commercial development. In addition to directly contributing to the educational development of students involved in the center's research, CaSTL organizes and participates in a variety of formal and informal science education activities, targeting audiences with varying educational backgrounds. Examples include summer schools for the broader chemistry community, the California State Summer School for Math and Science (COSMOS) aimed at high school students, and a variety of informal science education activities, such as an afterschool program at the Boys and Girls Club.During this funding period, CaSTL will continue development of an all-optical version of a working chemiscope, along with versions that combine optics with scan probe microscopes, and the ultimate observation of molecular motions and transformations on a femtosecond-Angstrom spatiotemporal scale. The group is moving toward application of this tool to specific chemical problems, in particular plasmon-enhanced photocatalysis. The excitation of collective electrons, the formation of hot electrons, their thermalization and scattering on interfaces, injection of electrons or holes into catalytic molecular centers and the subsequent breaking and making of bonds are targeted for capturing in space-time. Through time-resolved photoelectron emission microscopy (tr-PEEM) and 2-photon photoemission (tr-2PP) on catalytic metal clusters and hetero-structures, they are working to fully characterize the space-time dynamics initiated on the metal side upon excitation of plasmons. The complete time course of the photocatalyzed molecular transformation on the surface side is made possible using space-time-resolved surface-enhanced nonlinear coherent spectroscopy. Theoretical investigations are being used to guide the development and refinement of capabilities of this unique toolset. A complete understanding of photo-physics and chemistry ranging from small molecules implicated in catalysis to engineered mesoscale structures for devices is envisioned as a result of the center's work.