Vibrational energy in molecules probed with high time and space resolution

This article reviews experimental measurements of vibrational energy in condensed-phase molecules that simultaneously provide time resolution of picoseconds and spatial resolution of ångströms. In these measurements, ultrashort light pulses are used to input vibrational energy and probe dynamical processes. High spatial resolution is obtained using vibrational reporter groups in known locations on the molecules. Three examples are discussed in detail: (1) vibrational energy flow across molecules in a liquid from an OH-group to a CH₃-group; (2) vibrational energy flow across a molecular surfactant monolayer that separates an aqueous and a non-polar phase in a suspension of reverse micelles; and (3) vibrational energy input by laser-driven shock waves to a self-assembled monolayer of long-chain alkane molecules. These experiments provide new insights into the movement of mechanical energy over short length and time scales where ordinary concepts of heat conduction no longer apply, where the concepts of quantum mechanical energy transfer reign supreme.