Ahmed Zewail

Ahmed Zewail was an Egyptian-American chemist who founded the field of femtochemistry, the study of chemical reactions on the extraordinarily short timescale on which chemical bonds actually break and form. Working at the California Institute of Technology from the 1980s onward, Zewail developed techniques using extremely short pulses of laser light, each lasting only a few femtoseconds, or millionths of a billionth of a second, to effectively photograph the fleeting transition states that molecules pass through in the instant a chemical bond is breaking or forming, states that had previously been far too brief for any instrument to directly observe. This technique allowed chemists for the first time to watch, in something like slow motion, the actual physical process of a chemical reaction taking place at the level of individual atoms and molecules, rather than only inferring what must have happened from the reaction's starting materials and final products. Zewail was awarded the 1999 Nobel Prize in Chemistry for his studies of the transition states of chemical reactions using femtosecond spectroscopy, becoming the first Egyptian and the first Arab scientist to win a Nobel Prize in any scientific category. Later in his career Zewail extended these ultrafast techniques to develop four-dimensional electron microscopy, a method combining electron microscopy with femtosecond timing that let researchers image the motion of atoms roughly a billion times faster than had been possible with earlier microscope technology, and he remained active in science education and policy advocacy in Egypt and the broader Arab world throughout his career.