Simulation of the Absorption and Circular Dichroism Spectra for the Primary Electron Donor in Reaction Centers of Purple Bacteria and Photosystem II

1990 ◽  
pp. 377-388 ◽  
Author(s):  
A. Scherz ◽  
J. R. E. Fisher ◽  
P. Braun
Keyword(s):  
Circular Dichroism ◽  
Photosystem Ii ◽  
Electron Donor ◽  
Purple Bacteria ◽  
Primary Electron ◽  
Reaction Centers ◽  
Primary Electron Donor ◽  
Circular Dichroism Spectra ◽  
Circular Dichroïsm

scholarly journals Absorption and Circular Dichroism Spectra of Molecular Aggregates with the Full Cumulant Expansion.

2020 ◽  
Author(s):  
Lorenzo Cupellini ◽  
Filippo Lipparini ◽  
Jianshu Cao
Keyword(s):  
Circular Dichroism ◽  
Purple Bacteria ◽  
Spectroscopic Techniques ◽  
Molecular Aggregates ◽  
Cumulant Expansion ◽  
Circular Dichroism Spectra ◽  
Linear Absorption ◽  
Redfield Theory ◽  
Vibronic Sideband ◽  
Circular Dichroïsm

The exciton Hamiltonian of multichromophoric aggregates can be probed by spectroscopic techniques such as linear absorption and circular dichroism. In order to compare calculated Hamiltonians to experiments, a lineshape theory is needed, which takes into account the coupling of the excitons with inter- and intramolecular vibrations. This coupling is normally introduced in a perturbative way through the cumulant expansion formalism, and further approximated by assuming a Markovian exciton dynamics, for example with the modified Redfield theory.<br><br>Here we present an implementation of the full cumulant expansion (FCE) formalism [Ma and Cao, <i>J. Chem. Phys.</i> <b>2015</b>, 142, 094106 ] to efficiently compute absorption and circular dichroism spectra of molecular aggregates beyond the Markov approximation, without restrictions on the form of the exciton-phonon coupling. By employing the LH2 system of purple bacteria as a challenging test case, we compare the FCE lineshapes with the Markovian lineshapes obtained with the modified Redfield theory, showing that the latter present a much poorer agreement with experiments. The FCE approach instead accurately describes the lineshapes, especially in the vibronic sideband of the B800 peak. We envision that the FCE approach will become a valuable tool for accurately comparing model exciton Hamiltonians with optical spectroscopy experiments.

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