Ultrafast coherent spectroscopic investigation on photosynthetic pigment chlorophyll a utilizing 20 fs pulses

• Chlorophyll a is an essential pigment for oxygenic photosynthesis.
• Four-wave mixing spectroscopies using 20 fs pulses were applied to chlorophyll a.
• Real-time wave-packet motions of twelve vibrational modes were observed.

Vibrational dynamics of the photosynthetic pigment chlorophyll a in solution have been investigated by degenerated three-pulse four-wave mixing spectroscopies (transient grating and photon echo) using 20 fs pulses. Real-time wave-packet motions of intramolecular vibrations were clearly observed in four-wave mixing signals. Twelve vibrational modes due to chlorophyll a in the region of energy ranging from 200 to 1400 cm−1 were found in the Fourier transform power spectra of coherent oscillations. We demonstrate that a specific light–matter interaction can be enhanced by a control of the temporal separation between the first and second pulses.

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