How molecular vibrations make photosynthesis efficient
(july 13, 2015) Plants
and bacteria make use of sunlight with remarkably high efficiency: nine out of
ten absorbed light particles are being put to use in an ordinary bacterium. For
years, it has been a pressing question of modern research whether or not
effects from quantum physics are responsible for this outstanding performance
of natural light harvesters. A team of European research groups, a
collaboration between universities in Vienna, Ulm, Cartagena, Prague, Berlin
and Lund, have examined these quantum effects in an artificial model system. It
was shown that the hotly debated quantum phenomena can be understood as a
delicate interplay between vibrations and electrons of the involved molecules.
The resulting theoretical model explains the experiments perfectly. The article
was published in Nature Communications.
The studied artificial light harvester is a supramolecule,
consisting of hundreds of thousands of light absorbing molecules, arranged in
close proximity to one another and in an orderly fashion. Such architecture
puts these systems in between noisy living cells and strictly organized quantum
experiments at low temperatures: supramolecules are still governed by the same
quantum effects as natural photosynthetic systems, but without the noisy
background that makes their investigation so difficult in biological systems.
The research team employed polarized light to isolate the desired
quantum-dynamical effects. Studying such ordered systems does not only further
our understanding of natural photosynthesis, it also helps us to appreciate the
physical mechanisms necessary for energy-efficient, cheaper, more flexible and
lighter photovoltaic cells.