"Nature has designed one of the most exquisitely effective systems for harvesting light, with the steps happening too fast for energy to be wasted as heat," Fleming said. "Current solar power systems, however, aren't following Nature's model."
Emulating natural photosynthesis will require a better understanding of how energy gets transferred from light-absorbing pigment molecules to the molecules that make up the energy-converting reaction centers. Since the extra energy being transferred from one molecule to the next changes the way each absorbs and emits light, the flow of energy can be followed through optical spectroscopy, resolved on a femtosecond timescale.
Recently, a 2-D femtosecond spectroscopy technique using infrared light has been used to directly observe spatial arrangements of molecular systems that are vibrationally coupled. Fleming and his colleagues were able to extend this technique to electronic excitations which require visible light for their excitation. In this way, they were able to study the all-important changes and connectivity in the electronic states of these coupled molecular systems. They found two main energy transfer pathways in which some molecules were by-passed in the process because of insufficient spatial overlap with potential energy transfer partners. In one pathway, where there were seven potential energy transfer steps, the process was completed in three steps. In the other pathway, where there were six potential transfer ste
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Contact: Lynn Yarris
lcyarris@lbl.gov
510-486-5375
DOE/Lawrence Berkeley National Laboratory
31-Mar-2005