Gary Taubes, Discover Magazine, reports:
Understanding molecules, he’s quick to point out, is a prerequisite for understanding just about anything else. “Look at the world,” says Zewail. “Everything around us is chemical reactions. Everything–inside you and me, the atmosphere, everything we breathe, we touch. Everything is a chemical reaction. So we have to develop a unified theory of how chemistry takes place. We can’t understand this unless we really have a coherent understanding of how atoms and molecules like or dislike each other. That’s our ultimate goal.”
The catch is that these intimate chemical acts occur on a time scale that is almost unimaginably short: they take place in femtoseconds, to be precise, which are the quadrillionth parts of a second. A quadrillionth equals a thousand-trillionth, or .000000000000001; for perspective, you might contemplate that a femtosecond is to a second as a second is to 32 million years. To capture such acts as they happen requires having a strobe light fast enough to illuminate the action before it’s over, which begins to explain the reason for the lasers down in Femtoland.
Until Zewail came along, chemists had been unable to watch the making and breaking of molecules because they didn’t have a flashbulb capable of breaking time into femtosecond chunks–the scale of the reactions themselves. They had to settle for studying the before and after; the “during” was a blur. This situation, as one Swedish chemist put it, was analogous to trying to understand Hamlet while seeing only the introduction of the characters followed immediately by the closing scene, which is to say a stage set with “a considerable number of dead bodies and a few survivors.” Zewail managed to capture the mysterious acts in between, known in the lingo as transition states. These states mark the adjustments that must be made before two atoms that have lived as separate entities can be joined in a coupled pair that behaves as one–the courtship, if you will, between meeting and marriage–or conversely, the trauma that occupies the space between marriage and divorce. Zewail calls these states “the configurations of no return.”