Chemistry in a trillionth of a second

Chemists at the University of Bristol, in collaboration with colleagues at the Central Laser Facility at the Rutherford Appleton Laboratory (RAL) and Heriot-Watt University (HWU), can now follow chemical reactions in liquids with unprecedented, atomically resolved detail on sub-picosecond timescales (1 picosecond = 10-12s) - matching the time intervals between molecular collisions. Many important chemical processes occur in liquids, including the biochemistry of living organisms, the environmental chemistry in rivers, lakes and oceans, and the synthesis of drug molecules by the pharmaceutical industry. But, what really happens during these chemical transformations? Atoms and molecules are far too small to see, even using the world's best microscope. Moreover, in the close quarters of a liquid, each molecule experiences about ten trillion collisions every second. In work published today in Science, the researchers combine ultrafast laser spectroscopy in the infra-red spectral region and cutting-edge computer simulations to study the reaction of a fluorine (F) atom removing a deuterium (D) atom from an organic solvent molecule to make deuterium fluoride (DF). This type of reaction has been previously studied in detail in the gas phase, without the attendant complications of the surrounding solvent molecules. Differences in the outcome of the chemical reaction in a liquid therefore reflect the influence of the solvent on the reacting atoms and molecules.