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Femtochemistry

Femtochemistry. Chemistry on the 10 -15 Sec time scale!. A + B-C  A-B + C. Complete evolution of chemical event. Chemical reaction kinetics: Task of making a motion picture of a reaction. Difficulties of a movie-maker: Too many transient actors on the stage!!!!!.

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Femtochemistry

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  1. Femtochemistry Chemistry on the 10-15 Sec time scale! A + B-C  A-B + C Complete evolution of chemical event Chemical reaction kinetics: Task of making a motion picture of a reaction. Difficulties of a movie-maker: Too many transientactors on the stage!!!!! Making new bonds and breaking old ones: subpicosecond time scale. Femtosecond laser pulses : sub-angstrom motion could be watched!!!!!!

  2. Time scale of reactions Terminal velocities of separation of fragments A and BC ~ 0.01 Angstrom fs-1 ~104 – 105 cm/s Time required to break the bond ~ few 100 fs !!!! Saddle points

  3. Theoretical femtochemistry 1930: Evans, Polanyi & Eyring  concept of Transition state 1936: Hirschfelder, Eyring, and Topley H + H - H  H - H + H Flash photolysis with only ms (10-3 s) resolution in 1949 !!!

  4. The Royal Swedish Academy of Sciences has awarded the 1999 Nobel Prize in Chemistry to Professor Ahmed H. Zewail, California Institute of Technology, Pasadena, USA for showing that it is possible with rapid laser technique to see how atoms in a molecule move during a chemical reaction. The Academy's citation:For his studies of the transition states of chemical reactions using femtosecond spectroscopy.

  5. ------- Ahmed Zewail

  6. FTS Femtosecond Transition State Spectroscopy

  7. Femtosecond pump-probe spectroscopy

  8. ICNICN*[I…CN]* I + CN 1 2 (388.5 nm) (307 nm)

  9. The classical femtosecond ICN discovery

  10. Zewail’s Femtochemistry apparatus

  11. Femtochemistry set up

  12. Techniques for probing femtochemistry

  13. The Nobel Prize in Chemistry 1986 "for their contributions concerning the dynamics of chemical elementary processes" Dudley R. Herschbach Yuan T. Lee John C. Polanyi Harvard University Cambridge, MA, USA University of California Berkeley, CA, USA University of Toronto Toronto, Canada

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