Sponsored by Rohm and Haas
A revolution in spectroscopy is credited to Donald H. Levy, Albert A. Michelson Distinguished Service Professor at the University of Chicago. In fact, "his career has helped define modern molecular spectroscopy," comments one nominator.
Levy, 66, developed techniques for seeding molecules into supersonic expansions where collisions bring them into equilibrium with a narrow distribution of translational energies and, thus, cool their internal degrees of freedom to temperatures as low as a few kelvins. The approach has two important consequences: It removes spectral congestion by placing all of the population in the lowest quantum states, and it permits the formation of weakly bound molecules for spectroscopic study.
One of the first demonstrations of this approach to removing spectral congestion was Levy's simplification of the enormously complex spectrum of NO2 by cooling the molecules in an expansion. Today, spectroscopists routinely cool molecules to simplify spectra that would otherwise be incomprehensible. The technique is a "workhorse for spectroscopy all the way from the microwave region to ultraviolet and even X-ray wavelengths," a colleague writes. "Applications to biomolecules, which Don pioneered, are coming from several laboratories now."
Studies of the gas-phase spectroscopy of molecules such as amino acids and peptides that are not ordinarily observed in the gas phase are also of interest to Levy. He uses laser desorption to introduce them into a molecular beam and then study their properties spectroscopically. "These molecules are naturally occurring spectroscopic probes of biologically interesting systems." Levy writes.
Levy is interested, too, in studying the laser desorption process. "When a solid composed of large, fragile molecules is exposed to pulsed laser radiation, it is often possible to vaporize intact molecules as large as small proteins with no damage to the molecule. This is a striking and unintuitive phenomenon, and I am interested in understanding the mechanism by which it occurs," he says.
"An interest in spectroscopy is what drove me into chemistry," Levy continues. "At the time, it was about the only way of finding out what individual molecules were doing. The instrument and what it could do came as big news to me, and I wanted to find out more. I still do.
"I spent my time as a graduate student and as a postdoc doing various kinds of spectroscopy using microwaves," Levy continues. "We had been provided radiation sources that were bright, coherent, high-powered, monochromatic, and easily tunable. When I started doing electronic spectroscopy, this kind of source was clearly what you wanted to use, and that meant lasers. They weren't so tunable in those days, but anything was better than going back to an incoherent, broadband, low-powered lamp."
Levy holds a bachelor's degree in chemistry from Harvard University (1961) and a Ph.D. degree in chemistry from the University of California, Berkeley (1965). He held two postdoctoral fellowships at Cambridge University, England, before becoming an assistant professor of chemistry at the University of Chicago in 1967. He has been with that university ever since.
Levy is editor of the Journal of Chemical Physics and a member of the National Academy of Sciences and the American Academy of Arts & Sciences. He has published more than 180 research papers.
The award address will be presented before the Division of Physical Chemistry.—William Schulz