C. D. Lin Department of Physics, Kansas State University, USA Theory of Dynamic Chemical Imaging with infrared laser Pulses Time: Monday, May 25, 14.15 to 15.00 Place: Fysisk Auditorium When an infrared laser pulse interacts with atoms or molecules, electrons which are released earlier may be driven back by the laser field to recollide with the target ions. These recollisions incur the well-known strong field phenomena of high-order harmonic generation (HHG) as well as high-energy above-threshold ionization (HATI) photoelectrons. Since infrared laser pulses with duration of a few femtoseconds are now widely available, it is clear that HHG and HATI spectra can be used to extract the structural change of a transient molecule with temporal resolution of a few femtoseconds in a typical pump-probe setup. Based on the rescattering concept, recently we have established a quantitative rescattering theory (QRS) where the HHG yield can be expressed as the product of a returning electron wave packet with the photo-recombination cross section, and the HATI spectra can be expressed as the product of a similar wave packet with the elastic differential cross sections (DCS) between the target ion with free electrons. The QRS has now been applied to compare with experimental HHG spectra from molecules, from which molecular frame photoionization cross sections can be extracted. The QRS has also been applied to study the HATI spectra extensively to retrieve the DCS of electron-ion collisions. Using the extracted DCS for electron energies in the typical range of the returning electrons, we have shown that the target structure can be retrieved. From the returning electron wave packet, we can also obtain the laser parameters, including pulse duration, peak intensity and carrier-envelope-phase, from the measured HATI spectra. Peter Staanum and Nicolai Nygaard Coffee, tea and bread rolls will be served at 14.05 ---------------------------------- Peter Frøhlich Staanum Department of Physics and Astronomy University of Aarhus Ny Munkegade 120 8000 Aarhus C Denmark Phone: (+45) 8942 3602 Fax: (+45) 8612 0740 VAT Nr.: DK16562777 EAN Nr.: 5798000419872 ----------------------------------