Berlin 2005 – scientific programme

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MO: Molekülphysik

MO 43: Ultrafast Processes

MO 43.7: Talk

Tuesday, March 8, 2005, 18:00–18:15, HU 2091

Anharmonic couplings underlying ultrafast vibrational dynamics of acetic acid dimers — •N. Huse¹, B. D. Bruner², M. L. Cowan², J. Dreyer¹, E. T. J. Nibbering¹, R. J. D. Miller², and T. Elsaesser¹ — ¹Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie, Max-Born-Str. 2A, D-12489 Berlin, Germany — ²Departments of Physics and Chemistry, University of Toronto, 80 St. George St., Toronto, ON, M5S 3H6 Canada

Hydrogen bonded systems display strong anharmonic couplings between different vibrations resulting in complex vibrational spectra and dynamics. We analyze the line shape of the O-H stretching band of cyclic acetic acid dimers in solution, an important model system with two O-H...O bonds. Two-dimensional (2D) heterodyne detected photon echo spectroscopy based on a new diffractive optic (DO) technique [1] and on spectral interferometry are used to record the 2D infrared spectra. Signal Phase stability is better than λ/150. We find pronounced Fermi resonances between the O-H stretching v=1 level and combination/overtone levels of O-H bending, C-O and C=O stretching modes and multi-level quantum beats in the coupled low-frequency modes. Fermi resonance couplings of 40 to 150 cm⁻¹ are of similar strength as those of the low-frequency hydrogen bond stretching and in-plane deformation modes [2].