Photophysical hole burning in the resonance Raman excitation profile of the chlorophyll a dimer in solution

The Raman excitation profiles of normal modes of chlorophyll a dimers in hexane exhibit sharp minima between 427 and 450 nm. In this spectral range, a non-linear relationship between the Raman intensifies and the intensity of the pulsed laser is observed. These non-linearities indicate population of lower-lying excited states of the chlorophyll a dimer. The Raman scaterring from these excited states is weaker than the rigorous resonance-enhanced Raman scattering from the ground states, which leads to the observed minima.