Ahmed H. Zewail
Wolf Prize Laureate in Chemistry 1993
Ahmed H. Zewail
Affiliation at the time of the award:
California institute of Technology, USA
“for using ultrafast lasers in femtosecond time resolved measurements of the evolution of chemical reactions – thus obtaining the first direct observation of bond breakage in a molecule”.
Professor Ahmed H. Zewail has pioneered the development of femtosecond chemistry in molecular beams. With ultrafast lasers and molecular beam technology, Zewail´s landmark research is uncovering the real-time dynamics of chemical reactions at their most fundamental level. Quantum state-to-state rates, energy redistribution in molecules, and femtosecond spectroscopy, can now be observed directly.
With these techniques, Zewail has made major contributions to chemical physics in the following research areas:
Femtochemistry and transition states. With an ingenious time/wavelength technique for recording the femtosecond dynamics of a molecule in the process of falling apart, Zewail and coworkers have followed the transition region from reagent to products in a variety of reactions. For the first time, femtosecond real-time observations of wave-packet dynamics were made directly for bound, quasibound, repulsive, and saddle-point potentials.
Bimolecular reactions. Using real-time clocking of a bimolecular reaction initiated within a van der Waals complex, his studies provided a direct measurement of the lifetime of a collision complex.
Unimolecular reactions. His work on picosecond photofragment spectroscopy and state-to-state measurements of reaction rates in a variety of systems has provided critical tests of statistical and dynamical theories.
Intramolecular energy redistribution. Novel methods have been conceived and used by lewail for probing vibrational and rotational energy redistribution in molecules. This work has established the presence of coherence and selectivity of vibrational energy flow in large polyatomic molecules.
The development of femtosecond molecular beam chemistry by Zewail and his group has initiated the new field of real-time molecular reaction dynamics in this time regime. He has aptly coined the name “femtochemistry’ to this new field.