Femtosekunden zeitaufgelöste Vierwellenmisch-Techniken als Alternative zu herkömmlichen Anregungs-Abfrage-Schemata zur Analyse komplexer Moleküldynamik in der Gasphase

• Applicant: Professor Dr. Arnulf Materny
• Subject Area: Physical Chemistry of Molecules, Liquids and Interfaces, Biophysical Chemistry
• Term: from 2004 to 2009
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 5442668

• Final Report Year: 2008

Final Report Abstract

Ultrafast spectroscopy is one of the most active areas of research in chemical physics. Understanding the ultrafast behavior of molecules, and influencing it with the help of laser fields is of fundamental interest. This project work has focused on the investigation and control of molecular dynamics using time-resolved four-wave mixing (FWM) techniques in gas phase samples where molecules under ideal isolation axe available. Femtosecond FWM spectroscopy has established itself as a powerful tool to uncover molecular dynamics on ultrafast time scales. The femtosecond time resolution combined with a background-free, highly collimated coherent signal was demonstrated to make the approach unique for studying the dynamics especially under conditions of low concentrations. In gas phase, the elementary paths could be directly probed without the interference of solvent molecules. A comparative study of the molecular dynamics in the gas phase and condensed phase gave a detailed picture on the effect of environment. Utilization of Raman as well as optical resonances in FWM spectroscopy provided high selectivity with respect to the type of molecular dynamics observed in the transient signal. Schemes of FWM spectroscopy, which employed an initial pump pulse along with a fully time resolved FWM process, were devised to monitor also the dynamics of higher lying excited states. A feed back controlled optimization process in a FWM scheme was used, to selectively excite or suppress vibrational modes in gas phase and liquid phase of the same molecules.

Publications

• Femtosecond CARS on Molecules Exhibiting Ring Puckering Vibration in Gas and Liquid Phase. Chem. Phys. Lett. 433, 19 (2006)
  A. Scaria, J. Konradi, V. Namboodiri, M. Sackmann, A. Materny
  
• Vibrational Dynamics of Excited Electronic States of Molecular Iodine. J. Chem. Phys. 127, 144305 (2007)
  A. Scaria, V. Namboodiri, J. Konradi, and A. Materny
  
• A Comparison of the Selective Excitation of Molecular Modes in Gas and Liquid Phase Using Femtosecond Pulse Shaping.J. Raman Spectrosc. 39, 739 (2008)
  A. Scaria, V. Namboodiri, J. Konradi, and A. Materny
  
• Femtosecond Four- Wave Mixing for Investigation and Control of Molecular Gas Phase Dynamics in Different Electronic States. in Proceedings of the XXIst International Conference on Raman Spectroscopy, R. Withnall and B.Z. Chowdhry, eds. (IM Publications, Chichester, 2008), p. 279
  A. Materny, U. Kleinekathöfer, A. Scaria, V. Namboodiri, and J. Liebers
  
• Nonlinear Raman Techniques in Femtosecond Time Resolved Spectroscopy for the Analysis and Control of Molecular Dynamics. AIP Conf. Proc. 1075, 43 (2008)
  A. Materny, J. Konradi, V. Namboodiri, M. Namboodiri, and A. Scaria
  
• Ultrafast Vibrational Dynamics Observed in Higher Electronic Excited States of Iodine Using Pump-UV DFWM Spectroscopy, Phys. Chem,. Chem. Phys. 10, 983 (2008)
  A. Scaria, V. Namboodiri, J. Konradi, and A. Materny