Chemists glimpse the fleeting “transition state” of a reaction
During a chemical reaction, the molecules involved in the reaction gain energy until they reach a “point of no return” known as a transition state. Until now, no one has glimpsed this state, as it lasts for only a few femtoseconds (quadrillionths of a second). However, chemists at MIT, Argonne National Laboratory, and several other institutions have now devised a technique that allows them to determine the structure of the transition state by detailed observation of the products that result from the reaction. “We’re looking at the consequences of the event, which have encoded in them the actual structure of the transition state,” says Robert Field, the Robert T. Haslam and Bradley Dewey Professor of Chemistry at MIT. “It’s an indirect measurement, but it’s among the most direct classes of measurement that have been possible.” Field and his colleagues used millimeter-wave spectroscopy, which can measure the rotational-vibrational energy of reaction product molecules, to...