COHERENT PHENOMENA IN ULTRAFAST BIOLOGICAL PROCESSES

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An important question is whether the coherence introduced by optical excitation in the initial step of a light driven reaction is maintained during the primary process or not: Does the dynamics of the initially formed wavepacket on the reactive surface involve coherent motion? The observations of coherent wavepacket propagation provides an additional probe of the nature of the potential energy surface upon which the primary dynamical processes are occurring. It was decided to build a 16 fs time resolution pump/probe spectrometer capable of examining coherent propagation of wavepackets in large molecules incorporating vibrational excitations as large as ca. 1000 cm-1. This research is aimed at understanding wavepacket propagation processes and hence will focus on model systems initially, particularly systems undergoing electron transfer or isomerism. We would ask what is the participation of coherence in such processes. The reaction center is also a natural objective of this research. These experiments address how significant are coherent vibrational phenomena in ultrafast processes. However they are also expected to explore new ways of measuring and simulating coherent effects in proteins. This is a very new area of research and work on model compounds is being pursued (such as in porphyrin assemblies).