Zewail, Ahmed Hassan, 1946–, Egyptian-American chemist, Ph.D. Univ. of Pennsylvania, 1974. Zewail has been a professor at the California Institute of Technology since 1976. He was awarded the 1999 Nobel Prize in Chemistry for his use of femtosecond spectroscopy to study the transition states of chemical reactions. Using ultrashort laser flashes, Zewail investigated fundamental chemical reactions at the timescale on which they actually occur. His ability to observe the movement of individual atoms in a femtosecond, a millionth of a billionth of a second, brought about a new understanding of the dynamics of matter, with applications ranging from the design of molecular electronic components to the production of new medicines.