Ground-state vibrational coherence in chlorosomes of the green sulfur photosynthetic bacterium Chlorobium phaeobacteroides

Femtosecond transient absorption measurements have been performed on the bacteriochlorophyll e-containing chlorosomes of Chlorobium phaeobacteroides. Oscillations superimposed on the initial part of the kinetics and damped within 2 ps were observed. The Fourier power spectra revealed low-frequency vibrational modes in the range of 45–130 cm−1. The pump pulses centred at 425, 490 and 530 nm are in resonance with the S0–Sn transition, while the probe pulses between 710 and 785 nm monitor the S0–S1 transition. The observed oscillations can therefore be ascribed to ground-state vibrational coherence induced by resonant impulsive stimulated Raman scattering.