Coherent wavepacket motion in an ultrafast electron transfer system monitored by femtosecond degenerate four-wave-mixing and pump-probe spectroscopy

•Coherent wavepacket motion was investigated for ultrafast electron transfer (ET) system.•Vibrations originating from ground and excited states were extracted with high accuracy.•The dephasing of the excited state vibration was accelerated by the ultrafast ET.

Coherent nuclear wavepacket motions were monitored by three types of femtosecond time-resolved spectroscopy, namely, transient absorption measurement utilizing white-light supercontinuum (WC-TA), degenerate four-wave-mixing (DFWM), and pump-probe (PP) measurements, for an ultrafast intermolecular electron transfer (ET) system with a dye molecule, oxazine 1 (Ox1), dissolved in an electron donating solvent, N,N-dimethylaniline (DMA). Vibrational frequencies of the wavepacket motion in the excited and in the ground states were 560-562 and 567-569 cm−1, respectively, with only a few frequency difference of 5-9 cm−1, which were clearly distinguishable by the highly accurate measurements. In DMA, the excited state wavepacket motion declined with time constant of 160-240 fs which is somewhat longer than that of the ultrafast ET; 60-80 fs.

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