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.