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Excitonic Hamiltonians for Calculating Optical Absorption Spectra and Optoelectronic Properties of Molecular Aggregates and Solids
Published on: May 27, 2020
Single and multi-exciton dynamics in aqueous protochlorophyllide aggregates
Olga A Sytina1, Ivo H M van Stokkum, Rienk van Grondelle
1Department of Physics and Astronomy, Faculty of Sciences, Vrije Universiteit, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands.
The Journal of Physical Chemistry. A
|December 22, 2010
Summary
Protochlorophyllide (Pchlide) in water forms aggregates, influencing its excited state dynamics. Multiexciton states relax slowly into single-exciton states due to charge transfer and solvation effects.
Area of Science:
- Photosynthesis research
- Biophysics
- Spectroscopy
Background:
- Protochlorophyllide (Pchlide) is a precursor to chlorophyll, essential for photosynthesis.
- The enzyme POR catalyzes Pchlide reduction to chlorophyllide (Chlide) using NADPH.
- Light absorption by Pchlide initiates the reduction process.
Purpose of the Study:
- Investigate the excited state dynamics of Pchlide aggregates in water.
- Characterize multiexciton manifolds and their relaxation pathways.
- Understand the factors influencing exciton relaxation in Pchlide aggregates.
Main Methods:
- Ultrafast time-resolved transient absorption and fluorescence experiments.
- Visible (480-720 nm) and mid-IR (1780-1590 cm(-1)) spectroscopy.
- Absorption difference spectroscopy at varying photon densities.
Main Results:
- Aqueous Pchlide forms excitonically coupled aggregates with red-shifted absorption.
- Multiexciton states exhibit blue-shifted stimulated emission and red-shifted excited state absorption.
- Relaxation from multiexciton to one-exciton states occurs in approximately 10 ps.
Conclusions:
- Slow exciton relaxation is attributed to the charge transfer character of Pchlide excited states.
- Solvation stabilizes the charge transfer state, impacting recombination rates.
- These findings provide insights into light-harvesting and energy transfer mechanisms in Pchlide aggregates.
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