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Vibrational energy relaxation processes

Femtosecond two-colour pump-probe experiments in the mid-infrared demonstrate that excitation energy of the hydrogen-bonded O-H stretching oscillator of phthalic acid monomethyl ester is redistributed on a sub-picosecond time scale along the O-H bending vibration. The O-H stretching and O-H bending lifetimes are 220 and 800 fs, respectively. Quantum dynamical model calculations of the energy flow induced by O-H stretching excitation reveal a relaxation mechanism involving cascaded energy redistribution along the O-H bending vibration and two O-H out-of-plane deformation modes at about 700 and 800 cm-1. (Journal of Physical Chemistry A, 108, (2004), 6083).