Moved to 23 April: Prof. dr. R.J.D. Miller, Univ. of Toronto, Canada: "Making the Molecular Movie": First Frames
|22 April 2010||FWN-Building 5111.0080, Nijenborgh 4, 9747 AG, Groningen|
|Speaker:||Prof. dr. R.J. Dwayne Miller|
|Affiliation:||Institute for Optical Sciences, University of Toronto, Canada|
"Making the Molecular Movie": First Frames
Femtosecond Electron Diffraction has enabled atomic resolution to structural changes as they occur, essentially watching atoms move in real time ¾ directly observe transition states. This experiment has been referred to as "makingthe molecular movie" and has been previously discussed in the context of a gedanken experiment. With the recent development of femtosecondelectron pulses with sufficient number density to execute single shot structure determinations, this experiment has beenfinally realized. A new concept in electron pulse generation wasdeveloped based on a solution to the N-body electron propagationproblem involving up to 10,000 interacting electrons that has led toa new generation of extremely bright electron pulsed sources thatminimizes space charge broadening effects. Previously thoughtintractable problems of determining t=0 and fully characterizingelectron pulses on the femtosecond time scale have now beensolved through the use of the laser pondermotive potential to providea time dependent scattering source. Synchronization of electron probe and laser excitation pulses is now possible with an accuracy of 10 femtoseconds to follow even the fastest nuclear motions. The camera for the “molecular movie” is now in hand. Atomic level views of the simplest possible structural transition, melting, have been obtained for a number of systems involving both thermal and purely electronically driven atomic displacements. Optical manipulation of charge distributions and effects on interatomic forces/bonding can be directly observed. New phenomena involving cooperative phase transitions in strongly correlated electron systems have also been observed.The primitive origins of molecular cooperativity has also been discovered.These new developments will be discussed in the context of developing the necessary technology to directly observe the structure-function correlation in biomolecules ¾ the fundamental molecular basis of biological systems.
|Last modified:||12 September 2014 11.21 a.m.|