Hannover 2010 – wissenschaftliches Programm

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MO: Fachverband Molekülphysik

MO 5: Femtosecond Spectroscopy I

MO 5.4: Vortrag

Dienstag, 9. März 2010, 14:45–15:00, F 102

Investigation of intramolecular vibrational energy redistribution after overtone excitation of the CH-stretching vibration by femtosecond pump-probe experiments — •Alexander Kushnarenko, Vitaly Krylov, Eduard Miloglyadov, Martin Quack, and Georg Seyfang — Physical Chemistry Lab., ETH Zürich, Wolfgang-Pauli-Strasse 10, CH-8093 Zürich, Switzerland

Intramolecular vibrational energy redistribution (IVR) is essential for our understanding of intramolecular dynamics and for the theory of chemical reactions. One can derive the time evolution of the wavefunction theoretically from ab initio calculations and experimentally from high resolution IR-spectroscopy [1, 2]. The intramolecular dynamics can be measured directly in femtosecond pump-probe experiments in the gas phase [3], where after near-IR excitation the time dependence of the population of the initially excited level is obtained from the absorption of a delayed IR probe pulse. If a single excited molecular level is coupled to a dense set of background states a simple decay signal is obtained. However, in more complex cases oscillatory signals are measured and a decay may be superimposed. Using a hollow waveguide [3] we have investigated the IVR process for differently deuterated methyl iodides and fluorides and we have observed the phenomena mentioned.

[1] M. Quack, Chapt. 27 in “Femtosecond Chemistry”, J. Manz and L. Woeste, eds., Verlag Chemie (Weinheim, 1995) 781. [2] H. R. Dübal, M. Quack, J. Chem. Phys. 81, 3779 (1984). [3] V. Krylov, A. Kushnarenko, E. Miloglyadov, M. Quack, G. Seyfang, Proc. SPIE 6460, 64601D-1 (2007).