With support from the Chemical Mechanism, Function, and Properties (CMFP) program in the Division of Chemistry, Professors Andrew Musser and Phillip Milner of Cornell University are using ultrafast laser techniques to study how molecular coherence can be controlled. Coherence can arise when the electronic or vibrational states of two or more molecules synchronize, and it plays in central role in how light interacts with matter, from the physics of vision to photosynthesis to new systems for generating electricity from light. Proper control of such coherences could lead to devices that more efficiently harvest and transport energy, or to advanced applications of quantum mechanics in sensing and information science. And yet, despite its ubiquity, very little is known about how to tune such coherences or identify their unique contribution to photochemical processes. In this project, the teams of Musser and Milner will tackle this question in the context of singlet fission, a process in which one photoexcited state splits in two, with major implications for technologies such as quantum information science and light harvesting devices. Professor Milner and his students will prepare systematic libraries of crystalline sponge-like materials known as metal-organic frameworks – effectively molecular tinker toys whose modularity lets the team dial in specific interactions between photoactive molecules. Professor Musser and his students will use cutting-edge ultrafast laser-based measur