Sponsored by the General Electric Fund and the General Electric Corporate Research & Development Center
F. Fleming Crim Jr., John E. Willard Professor of Chemistry at the University of Wisconsin, Madison, has turned a relatively simple idea—examining how vibrational energy influences molecules—into profound success.
Crim, 58, started to study vibrational energy flows in molecules in the 1970s. "Everybody knew in the 1970s that vibrations were very important in chemical reactions, and we were trying to understand how vibrational energy got in and out of the molecule," he recalls.
Later, lasers became readily available in the laboratory as a means to excite the molecules into vibrational states. "It was an obvious intellectual opportunity to go after using them to drive reactions," Crim says. Early attempts at such applications were frustrated by systems in which the energy flowed around the molecules too rapidly to study. Crim's group seized on water, known to have relatively isolated vibrations, and conducted photodissociation experiments on it.
These experiments led to work in which Crim and coworkers used a chemical reaction to cleave a bond selectively, much as they had done with light. "His experiments are more than just novel; they are revolutionary," says James L. Skinner, a professor of chemistry at the University of Wisconsin. "Using electronic excitation along with vibrational overtone excitation, Crim and his coworkers demonstrated that photodissociation of highly vibrationally excited molecules produces entirely new behavior and provides a means of controlled cleavage of chemical bonds," Skinner says.
For example, Skinner continues, experimenting with CH3D, Crim's group was able to selectively cleave either the C-D bond or a C-H bond. "They also proved that molecules with excited symmetric stretching vibrations are six times more reactive than those with excited antisymmetric vibrations."
Another colleague agrees. Crim's "more recent work on bond-selective chemistry launched him into a select group of people doing the best physical chemistry in the world," he says.
Crim is more modest. He says the work provides a key to understanding certain reactions and is a means to control chemistry by using light. "The notion of controlling a reaction is a reflection of understanding the reaction," he says.
Lately, Crim's group has been focusing its attention on liquid systems in which molecules interact with solvents, instead of the more straightforward gaseous systems that the group had worked with previously.
Crim says growing up during the Sputnik era, when science was idealized, nurtured his interest in both physics and chemistry. A professor at Southwestern University inspired him to choose a career in chemistry. At Cornell University, where he earned his Ph.D., he learned that physical chemistry is a combination of two fields that he found deeply engrossing.
Crim joined the department of chemistry at Wisconsin in 1977 after serving with Los Alamos Scientific Laboratory and Western Electric. He became a member of the National Academy of Sciences in 2001. He has authored or coauthored more than 125 papers.
The award address will be presented before the Division of Physical Chemistry.—Alex Tullo