the objective of the seminar the objective of this seminar is to give a birds eye view on the topic...
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The objective of the seminar
The objective of this seminar is to give a bird’s eye view on the topic of Femtochemistry.
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Femtochemistry
The End of the Road
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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)
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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 .
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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 .
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Why do we need a fs?
Calculation of the speed of atomic motion 1 km/s i.e. 1m/10-3 sAtomic distances about 0.1 nmi.e. it takes 100x10-15 s (100 fs ) [1fs =10 -15 s ; ] [1fs to 1s is as 1s to 32 millions yrs ]
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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
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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)
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The end of the ROAD
With femtosecond spectroscopy we have reached the end of the road.
NO CHEMICAL REACTIONS TAKE PLACE FASTER THAN THIS!
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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 .(
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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
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Unifying disciplines
* Professor Zewail is now a professor of chemistry , a professor of physics and the
director of the institute of physical Biology .