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MO: Fachverband Molekülphysik

MO 8: Femtosekundenspektroskopie 2

MO 8.2: Vortrag

Dienstag, 3. März 2009, 14:15–14:30, VMP 6 HS-F

Probing intramolecular vibrational energy redistribution by time delayed femtosecond IR- and UV-absorption — •Alexander Kushnarenko, Vitaly Krylov, Eduard Miloglyadov, Martin Quack, and Georg Seyfang — Physical Chemistry Lab., ETH Zürich, Wolfgang-Pauli-Strasse 10, CH-8093 Zürich

Intramolecular vibrational energy redistribution (IVR) is essential for our understanding of molecular dynamics [1]. The time evolution of the vibrational wavefunction can be obtained from high-resolution IR-spectra or the IVR process can be studied directly in femtosecond pump-probe experiments [1-3]. We have set up a pump-probe scheme where for an increased sensitivity in the gas phase the two laser beams are confined in a hollow waveguide. In accordance with the prediction from IR-spectroscopy [2] our experiments show for propargyl-halides that the measured IVR times are larger by a factor 20 to 40 after excitation of the first overtone of the acetylenic CH-stretching vibration than the shortest time process detected after the excitation of the first overtone of the methylenic CH-stretching vibration. Investigations of IVR in the methyliodide and its deuterated isotopomers show a complex dynamics, strongly dependent on excitation frequency, that results from different coupling schemes for the excited CH-overtones.

[1] M. Quack, Chapt. 27 in ’Femtosecond Chemistry’, J. Manz and L. Woeste, eds, Verlag Chemie (Weinheim, 1995) 781. [2] K. v. Puttkamer, H. R. Dübal, M. Quack, Chem. Phys. Lett. 95, 358 (1983). [3] V. Krylov, A. Kushnarenko, E. Miloglyadov, M. Quack, G. Seyfang, Proc. SPIE 6460, 64601D (2007).