Assignment of the Q-bands of the Chlorophylls: Coherence Loss Via Qx - Qy Mixing

Overview

Journal Sci Rep

Specialty Science

Date 2013 Sep 27

PMID 24067303

Citations 31

Authors

Jeffrey R Reimers

Zheng-Li Cai

Rika Kobayashi

Margus Ratsep

Arvi Freiberg

Elmars Krausz

Affiliations

Soon will be listed here.

Abstract

We provide a new and definitive spectral assignment for the absorption, emission, high-resolution fluorescence excitation, linear dichroism, and/or magnetic circular dichroism spectra of 32 chlorophyllides in various environments. This encompases all data used to justify previous assignments and provides a simple interpretation of unexplained complex decoherence phenomena associated with Qx → Qy relaxation. Whilst most chlorophylls conform to the Gouterman model and display two independent transitions Qx (S2) and Qy (S1), strong vibronic coupling inseparably mixes these states in chlorophyll-a. This spreads x-polarized absorption intensity over the entire Q-band system to influence all exciton-transport, relaxation and coherence properties of chlorophyll-based photosystems. The fraction of the total absorption intensity attributed to Qx ranges between 7% and 33%, depending on chlorophyllide and coordination, and is between 10% and 25% for chlorophyll-a. CAM-B3LYP density-functional-theory calculations of the band origins, relative intensities, vibrational Huang-Rhys factors, and vibronic coupling strengths fully support this new assignment.

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