CHEMISTRY: Lives of Spirit and Dedication

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The call came to Boston Dentist James Hirshberg at 8:30 last Wednesday morning. It was from the Royal Swedish Academy of Sciences, saying he had won the Nobel Prize. But no, they had the wrong number. Then a radio station telephoned to congratulate Georgene Herschbach, a Harvard assistant dean. This was a mistake too, but at least the station was warm: she ran across the campus to her husband's office. So it was that Dudley R. Herschbach, 54, learned he would share this year's chemistry prize with his onetime collaborator, Yuan T. Lee, 49, of the University of California, Berkeley, and with John C. Polanyi, 57, a University of Toronto chemist.

The three were cited for developing methods that have revealed the most basic mechanisms of chemical reactions. To construct theories of what happens when chemicals react, scientists, prior to the laureates' work, had only sketchy evidence: the chemical products and the amount of energy produced or consumed by the end of a multistep reaction. But these observations gave information only about the net effect on millions of molecules; the changes that occur to individual molecules at each step stayed a mystery.

In the late 1950s Herschbach proposed to study what happens to individual molecules in the trillionth of a second of a chemical reaction by using the crossed molecular beam technique. Colleagues thought he was crazy, but this novel approach proved to be useful -- especially in the following years, when Lee made improvements that substantially increased the variety of reactions that could be studied this way. The method is analogous to that of particle physicists, who accelerate beams of speeding subatomic particles, smash them together or into a target, and then study the resulting debris. Herschbach's and Lee's beams consist of molecules instead of subatomic particles; when the molecules collide at about the speed of sound, they react to form new molecules, which spray in different directions. By looking at what new molecules have been formed, where they end up and what kind of energy is emitted or absorbed, chemists can reconstruct what happened in individual reactions.

Herschbach likens the problem to "the crowd at a baseball game. You really want to know what is being said by a few people at once -- the chemistry of individual 'conversations' between molecules." His method provides a way to acquire that knowledge, he said, which helps in understanding "the psychology of the mob."

Polanyi took a different approach. He studied chemical reactions by analyzing the faint infrared light emitted when molecules link up to form new substances, a phenomenon known as chemiluminescence. Says Polanyi: "You can see the dance of the molecules as they break up and are created." One application: the radiation can be amplified to produce a powerful new class of lasers.