Dr. H.J. Wörner
Joint Laboratory for Attosecond Science
National Research Council of
Monday, February 8, 2010
Following Chemical Reactions Using High-Harmonic Interferometry
One of the main goals of modern ultrafast science is to image a chemical reaction as it occurs. Recently, laser-induced recollision has demonstrated that imaging of both the nuclear and electronic structure of a static molecule is simultaneously possible [1,2]. In this talk, we apply these new methods to the time-resolved observation of chemical reactions . The coherence of high-harmonic generation turns the unavoidably low fraction of excited molecules into an advantage as the unexcited molecules act as a local oscillator. The application of the transient grating technique allows us to measure both amplitude and phase of the excited state emission and its evolution on the femtosecond time scale . Using the photodissociation of Br2 as an example, we show that the high-harmonic amplitude encodes the internuclear separation by quantum interference at short times and scattering of the photoelectrons at longer times. The high-harmonic phase records the attosecond dynamics of the electron. We will discuss how high-harmonic spectroscopy can be used in the future to investigate non-adiabatic molecular dynamics, image electronic ring currents and attosecond charge transport along molecular chains.
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 V. H. Le, A.-T. Le, R. H. Xie and C. D. Lin, Phys. Rev. A 76, 013414 (2007)
 H. J. Wörner, J. B. Bertrand, D. V. Kartashov, P. B. Corkum and D. M. Villeneuve, Nature (submitted)