The objective of the seminar The objective of this seminar is to give a birds eye view on the topic of Femtochemistry. The objective of this seminar is to give a birds eye view on the topic of Femtochemistry.

Femtochemistry The End of the Road

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

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.

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.

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

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

Race against time (1) Before a century time scale was (decade, yr, month, day, hr., s ) (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), (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) 1974( sub.ps),1987 (fs)

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

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

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

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