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The objective of the seminar

The objective of the seminar. The objective of this seminar is to give a bird’s eye view on the topic of Femtochemistry. Femtochemistry. The End of the Road. Definition.

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The objective of the seminar

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  1. The objective of the seminar • The objective of this seminar is to give a bird’s eye view on the topic of Femtochemistry.

  2. Femtochemistry The End of the Road

  3. Definition • Femtochemistry is the area of physical chemistry that studies chemical reactions on extremely short time scales , approximately 10-15 seconds (one femtosecond , hence the name)

  4. The date of birth : 1987 The Founder : Professor Ahmed Hassan Zewail Declaration and recognition : Professor Zewail was awarded the 1999 Noble Prize in Chemistry for showing that it is possible with rapid laser technique to see how atoms in a molecule move during a chemical reaction .

  5. The Theory The chemical reaction events at the microscopic level 1- The actual atomic motions in a chemical reaction have never been observed (2000 yrs) 2- During a chemical reaction : (i) bonds break (ii) bonds formed (iii) bonds geometrically change These processes are ultrafast .

  6. Why do we need a fs ? • Calculation of the speed of atomic motion • 1 km/s i.e. 1m/10-3 s • Atomic distances about 0.1 nm • i.e. it takes 100x10-15 s (100 fs ) • [ 1fs =10 -15 s ] ; • [1fs to 1s is as • 1s to 32 millions yrs ]

  7. The challenge is to “see” such an event !!! • To succeed we need : • (1) Time-resolution (fs) to freeze structures before any vibration or rotation takes place • (2) Time reference – the Cs clock • (3) Atomic-scale resolution (0.1 nm ) • (4) Transition from kinetics to dynamics • (5) Heisenberg uncertainty principle

  8. Race against time • (1) Before a century time scale was (decade, yr , month , day , hr. , s ) • (2) In the last 100 yrs time resolution witnessed major strides ; 1923(10-3 s flow systems ),1950 (10-6 s flash photolysis –ESR), 1960 (ns), 1966(ps), • 1974( sub.ps),1987 (fs)

  9. The end of the ROAD • With femtosecond spectroscopy we have reached the end of the road . • NO CHEMICAL REACTIONS TAKE PLACE FASTER THAN THIS !

  10. Experiment • Femtochemistry exploits the pump – probe technique : (i) A pump laser pulse initiates the chemical reaction. (ii) The probe laser pulse records a snapshot of the chemical reaction . why Lasers ? 1- well – defined λ 2- short pulse ( same λ , coherent phase , polarization ).

  11. PROFESSOR : AHMED ZEWAILTHE KING OF FEMTOCHEMISTRY • * NATIONALITY : EGYPTIAN AND AMERICAN • * BORN IN 1946 , DAMANHOUR ,EGYPT • * B.S., U. OF ALEXANDRIA, EGYPT (1967) • * M.S., U. OF ALEXANDRIA, EGYPT (1969) • * Ph.D. U. OF PENNSYLVANIA, U.S.A. (1974) • * PROFESSOR OF CHEMISTRY • * PROFESSOR OF PHYSICS • * DIRECOR OF PHYSICAL BIOLOGY CENTER FOR ULTRAFAST SCIENCE & TECHNOLOGY AT CALTECH • * PRESIDENT OBAMA COUNCIL OF ADVISERS ON SCIENE AND TECHNOLOGY • * FIRST UNITED STATES SCIENCE ENVOY TO THE MIDDLE EAST • * AUTHOR OF 14 BOOKS AND 554 PUBLISHED PAPAERS

  12. Unifying disciplines * Professor Zewail is now a professor of chemistry , a professor of physics and the director of the institute of physical Biology.

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