Tuesday, October 19, 1999 Volume 46 Number 8 www.upenn.edu/almanac/

Nobel Prize in Chemistry: Dr. Zewail, G'74 Dr. Ahmed H. Zewail, the Linus Pauling Professor at CalTech who took his Ph.D. at Penn in 1974, has won the 1999 Nobel Prize in Chemistry for his work leading to the birth of the field of femtochemistry--a breakthrough that has allowed high--speed cameras to take pictures of molecules in the process of undergoing chemical reactions. When he accepts the $950,000 award of the Royal Swedish Academy of Sciences in Stockholm on December 10, he will be the second Penn alumnus in three years to win the Prize.* Dr. Zewail is a dual citizen of the U.S. and of Egypt, where he was born in 1946. After taking his first academic degrees at Alexandria University--a B.S. in 1967 and M.S. in 1969--he came to the U.S. to study for his doctorate at Penn, working with Dr. Robin Hochstrasser, then Blanchard Professor and now the Donner Professor of Physical Sciences. "He was a very good student," recalls Dr. Hochstrasser. "He was always seeking research avenues that would take him into new territory. He did this as a student and continued with the same approach later. It was clear from the beginning that he had the potential for an outstanding research career. His femtosecond laser experiments on the synchronous excitation of small molecules have had a tremendous impact on chemistry and on the way in which chemists picture a molecule in the process of undergoing a chemical reaction." After completing his Ph.D., Dr. Zewail spent a year at Berkeley as an IBM Research Fellow, then joined the faculty at CalTech in 1976. He was tenured two years later, and became a full professor in 1982. He succeeded in 1990 to the Linus Pauling Chair of Chemistry, and he continues also as a professor of physics. His articles and books now number some 300. The work that has won him the Nobel Prize has already been widely recognized by the world scientific community. Among his many honors are the Robert A. Welch Prize Award, Wolf Prize, King Faisal Prize, Benjamin Franklin Medal, Leonardo Da Vinci Award of Excellence, Röntgen Prize, Paul Karrer Gold Medal, Bonner Chemiepreis, Medal of the Royal Netherlands Academy of Arts and Sciences, Carl Zeiss Award, Hoechst Award, and the Alexander von Humboldt Award--along with numerous prizes of the American Physical Society and American Chemical Society, the National Academy of Sciences, and others. A member of the National Academy and a host of honor societies, he has also been a Sloan Fellow, a Guggenheim Fellow, and a Camille and Henry Dreyfus Teacher-Scholar.    The U.S. government has awarded him the E.O. Lawrence Award; Egypt's President Mubarak conferred on him the Order of Merit, first class, in 1995; and last year Egypt issued two postage stamps in his honor, an accolade that touched him, as he told the Pennsylvania Gazette, by putting him "in the company of stamps honoring the pyramids, Tutankhamen and Queen Nefertiti." In 1997 Dr. Zewail came back to Penn for an honorary degree--one of six he now holds--and his citation said, in part, "The world scientific community has applauded your remarkable achievements, heaping upon you its highest honors...Your greatest honor, however, and the true measure of your profound effect upon the field will be found in the accomplishments of those who build upon your work." _____________ * For the 1997 Prize to Dr. Stanley Prusiner, C '64, M'68, see Almanac October 7, 1997.

Capturing the Femtosecond What would a football match on TV be without "slow motion" revealing afterwards the movements of the players and the ball when a goal is scored? Chemical reactions are a similar case. The chemists' eagerness to be able to follow chemical reactions in the greatest detail has prompted increasingly advanced technology. This year's laureate in Chemistry, Ahmed H. Zewail, has studied atoms and molecules in "slow motion" during a reaction and seen what actually happens when chemical bonds break and new ones are created. Zewail's technique uses what may be described as the world's fastest camera. This uses laser flashes of such short duration that we are down to the time scale on which the reactions actually happen--femtoseconds (fs). One femtosecond is 10-15 seconds, that is, 0.000000000000001 seconds, which is to a second as a second is to 32 million years. This area of physical chemistry has been named femtochemistry. Femtochemistry enables us to understand why certain chemical reactions take place but not others. We can also explain why the speed and yield of reactions depend on temperature. Scientists the world over are studying processes with femtosecond spectroscopy in gases, in fluids and in solids, on surfaces and in polymers. Applications range from how catalysts function and how molecular electronic components must be designed, to the most delicate mechanisms in life processes and how the medicines of the future should be produced. --From the Academy's Press Release

Almanac, Vol. 46, No. 8, October 19, 1999

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