Excited state dynamics of chromophores in glasses and in photosynthetic proteins

The optical properties of molecules dissolved in glasses and ligated to proteins are very similar. The technique of three pulse stimulated photon echo peak shift is used to explore these properties. For dilute chromophores in a glass, a model of linear coupling to a harmonic bath combined with temperature-independent inhomogeneous broadening works well from 30 to 300 K. For concentrated chromophores, such as exist in photosynthetic light harvesting complexes, energy transfer changes the appearance of the peak shift data. The timescale of energy transfer can be extracted from the peak shift data, along with the coupling to the protein and the width of the inhomogeneous distribution.