Excited Vibrations in Product Modes

The Fourier transforms as well as the fitting procedure reveal, depending on the molecule, two to four relevant frequencies below 700 cm in the oscillatory signal contributions (see Fig. 11.6 and Fig. 11.7). The oscillations extend to some picoseconds. Obviously the vibrational dephasing occurs on a picosecond time scale 

For the vibration with the lowest frequency (113 cm ) the phase corresponds to a starting time shifted by a quarter of a vibrational period relative to the configuration change. Apparently, the molecule is initially accelerated along this coordinate. 

The mode is a bending motion of the entire molecule which reduces primarily the proton donor-acceptor distance and introduces only slight changes in other parameters (see Fig. 11.10). A coherent excitation of very similar vibrational modes was found in all ESIPT molecules we investigated and also in DHAQ [30], BBXHQ [31], and 10-HBQ [32]. In HBT and HBO this mode also modulates the 

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