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Scholarly Article Template
  • Ashkan Roozbeh
Ashkan Roozbeh
Swinburne University of Technology
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Abstract

Photosynthetic light-harvesting complexes utilise a sophisticated mechanism at the quantum mechanical level to harvest and transfer sun's energy.  Following the observation of coherence signals in a wide range of photosynthetic antennae, which persist for unexpectedly long time scale after excitation with ultra-short laser pulses,  several theoretical and experimental efforts have been undertaken to  highlight/determine the nature of the observed coherence signalst. Generally,  CMDS   measurements that have been performed on light-harvesting complexes, rely on using broadband laser pulses to excite and probe the sample. Although this provide rich in information spectra, population dynamics as well as coherent superposition can be excited and contribute in the signal. Hence, since a single physical phenomenon is not isolated in these experiments, the interpretation and determining the nature of the subtle features in the resultant 2D spectra can be controversial. Therefore, a lot of effort has been made to better decode  the information presented in ”2D spectra” and work out the significance of those observations for light harvesting using different techniques. Determining the nature of the observed features is important as it leads to different energy transfer theories to emerge and affects our understanding of system-bath interactions, interplay between electronic excitation and vibrations and the energy transfer process in photosynthetic proteins. Here, we use both broadband and pathway selective coherent multidimensional spectroscopy using spectrally tailored pulses to  explore the photophysiscs of the light-harvesting complex PC645 following the excitation using the ultrashort pulses. Using Pathway selection and different excitation schemes and previous observations, we determine the nature and the pathways responsible for the observed coherences in 2D spectra.