Ultrafast Infra-red Spectroscopy as a Probe of Chemical Reaction Mechanisms

The timescales for reactions in solution are very fast, with lifetimes of reactive or energized intermediates that can be as short as a few picoseconds.  Nevertheless, these intermediates can be observed, and the flow of energy released by exothermic reactions can be followed using techniques based on ultrafast infra-red spectroscopy.  Two-dimensional infra-red spectroscopy (2DIR) provides further insights into structural changes and energy flow in molecules on these very short timescales.  This talk will introduce the techniques of ultrafast time resolved infra-red and 2DIR spectroscopy and illustrate their application to the study of the mechanisms of chemical reactions.  Examples will be drawn from our work on radical reactions in solution, photochemistry of hydrogen-bonded DNA base pairs, and vibrational dynamics in transition metal complexes.