I’ve recently been involved in a collaboration with members of the Bristol laser group. They used ultrafast infrared lasers to watch real-time product formation for a chemical reaction occurring in a liquid. Their time resolution was on the order of picosecsonds (10^-12 seconds), which allowed them to watch reaction products being produced in an excited vibrational quantum state. I was able to rationalize their experiments by showing that the gas and liquid phase reaction free energy profiles are more similar than had previously been supposed. Thus, at very short times – on the order of ~10 picoseconds – the reaction in a liquid proceeds more or less identically to what happens in a low pressure gas. This work has been funded by the EPSRC, and is featured on the cover of the 18th March issue of Science, with follow-up publications to appear shortly. Click here to view some movies of how the reaction proceeds in both a gas and a liquid.

The left and right hand graphics show overlays of the CN + cyclohexane geometries at the point where they pass over their respective transition states in a gas and in a liquid (dichloromethane). Their similarity explains in part, why at short times, the gas phase quantum state specificity carries over to liquids.