In this project supported by the Experimental Physical Chemistry Program of the Chemistry Division, Chan will use pressure as an experimental parameter to elucidate the nature of dynamic processes, such as a physical interaction or a chemical reaction, in the condensed phase. A diamond anvil cell (DAC) is used to introduce pressure at temperatures down to 4 K, and systems are probed using emission lifetime, transient absorption, and high-pressure laser spectroscopy. Studies of quantum tunneling reactions and experiments on energy transport in quasi one-dimensional spectroscopic systems will be performed. Pressure offers a useful new dimension in chemical investigation because it provides a controlled and gradual means to modify molecular distance and orientation. In these experiments two diamond anvils compress a small hole in a gasket and generate very high pressure under conditions of very low temperatures. Results from this project will help illuminate reactivity in the solid-state and will have practical implications in understanding the photophysics of dye aggregates, such as are important in the technology of photography.