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Dr. Leonardo Banchi

ISI Foundation, Turin

Tuesday, January 8th, 2013 at 11:30:00 AM  

Conference room Querzoli - LENS - via Nello Carrara 1 - Sesto Fiorentino (Florence)

Published on-line at 10:55:52 AM on Monday, January 7th, 2013

On the adequacy of multichromophoric Förster theory to the study of energy transfer in light harvesting complexes

An analysis of the multi-chromophoric Förster theory application to pigment-protein complexes.

Light harvesting complexes are difficult to model in a quantum mechanical fashion because of their strong interaction with the surrounding environment. Standard approximations used to face open quantum systems dynamics rest on quantum master equation techniques, based on a weak coupling assumption between the investigated system and the unknown thermal environment, or on Förster theory, a classical-like description, accurate in the opposite limit, where the electronic delocalization of the excitons amongst different pigments is completely neglected. As a matter of fact, in pigment-protein complexes (PPC) the strength of the interaction with the thermal environment is of the same order of the electronic couplings, and perturbative expansions are, in principle, not justified, whereas numerically exact techniques need heavy computational resources even for simulating small systems.

In the last decade a new theory, called multi-chromophoric Förster theory (MCFT) has been developed. In MCFT the network of pigments is divided into aggregates, i.e. subnetworks of strongly interacting chromophores. Instead of considering a full quantum description or a classical-like treatment of the transfer process, in MCFT the approximation is to model the transfer between different aggregates using classical-like rates, whilst the dynamics inside the aggregate is treated quantum mechanically.

In this talk we analyse the regimes of validity of this theory for some simple PPC by comparing the results of MCFT with those of a numerically exact method (hierarchical approach).

For further informations, please contact Dr. Filippo Caruso.