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MO: Molekülphysik
MO 14: Femtosekundenspektroskopie V: molekulare Schwingungen
MO 14.4: Vortrag
Donnerstag, 7. März 2002, 14:45–15:00, HS 15/E07
Femtosecond mid-infrared photon echo peak shift study of water — •Jens Stenger1, Dorte Madsen1, Peter Hamm1,2, Erik T. J. Nibbering1, and Thomas Elsaesser1 — 1Max Born Institut fuer Nichtlineare Optik und Kurzzeitspektroskopie, Berlin-Adlershof — 2Physikalisch Chemisches Institut, Universitaet Zuerich, Switzerland
Femtosecond mid-infrared photon echo spectroscopy enables one to decipher the dephasing and spectral diffusion dynamics of vibrational transitions, giving direct access to solute-solvent coupling strength and fluctuations of hydrogen bonds in liquids. We present the first photon echo peak shift study of the prototypical hydrogen bonded network, liquid water, by studying the O-H stretching vibration in HDO in deuterated water. The solvent fluctuation correlation function consists of components on may time scales. An ultrafast component leads to an ultrarapid dephasing time of 90 fs, as shown by the two pulse photon echo decay [1], whereas the three pulse photon echo peak shift (3PEPS) signal has contributions with picosecond time scales. Fluctuations of local structure of the hydrogen bond network are found to be relatively long lived. Vibrational relaxation of the excited-state of the O-H stretching mode populates a state that is spectroscopically different, thereby strongly altering the 3PEPS signal. As a consequence the 3PEPS signal does not mimic directly the fluctuation correlation function. [1]. Stenger et. al, Phys. Rev. Lett. 87, 027401 (2001).