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Non-radiative relaxation of photoexcited chlorophylls: theoretical and experimental study.

Bricker WP, Shenai PM, Ghosh A, Liu Z, Enriquez MG, Lambrev PH, Tan HS, Lo CS, Tretiak S, Fernandez-Alberti S, Zhao Y - Sci Rep (2015)

Bottom Line: Nonradiative relaxation of high-energy excited states to the lowest excited state in chlorophylls marks the first step in the process of photosynthesis.Modeling this process with non-adiabatic excited state molecular dynamics simulations uncovers a critical role played by the different side groups in the two molecules in governing the intramolecular redistribution of excited state wavefunction, leading, in turn, to different time-scales.This is achieved via selective participation of specific atomic groups and complex global migration of the wavefunction from the outer to inner ring, which may have important implications for biological light-harvesting function.

View Article: PubMed Central - PubMed

Affiliation: Department of Energy, Environmental and Chemical Engineering, Washington University, Saint Louis, Missouri 63130, USA.

ABSTRACT
Nonradiative relaxation of high-energy excited states to the lowest excited state in chlorophylls marks the first step in the process of photosynthesis. We perform ultrafast transient absorption spectroscopy measurements, that reveal this internal conversion dynamics to be slightly slower in chlorophyll B than in chlorophyll A. Modeling this process with non-adiabatic excited state molecular dynamics simulations uncovers a critical role played by the different side groups in the two molecules in governing the intramolecular redistribution of excited state wavefunction, leading, in turn, to different time-scales. Even given smaller electron-vibrational couplings compared to common organic conjugated chromophores, these molecules are able to efficiently dissipate about 1 eV of electronic energy into heat on the timescale of around 200 fs. This is achieved via selective participation of specific atomic groups and complex global migration of the wavefunction from the outer to inner ring, which may have important implications for biological light-harvesting function.

No MeSH data available.


Related in: MedlinePlus

Averaged excited state populations of Qy (red), Qx (green), and B (blue) bands in (a) ChlA and (b) ChlB species during a 500 trajectory nonadiabatic excited-state molecular dynamics (NA-ESMD) simulation (Sim).Population model fit (first-order, irreversible) is also shown for Qy, Qx, and B bands (Fit). The excited state simulations were run for 1 ps, and began with an excitation pulse centered around the B band.
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f5: Averaged excited state populations of Qy (red), Qx (green), and B (blue) bands in (a) ChlA and (b) ChlB species during a 500 trajectory nonadiabatic excited-state molecular dynamics (NA-ESMD) simulation (Sim).Population model fit (first-order, irreversible) is also shown for Qy, Qx, and B bands (Fit). The excited state simulations were run for 1 ps, and began with an excitation pulse centered around the B band.

Mentions: After initial excitation in the red edge of the B band of the two chlorophyll species, we calculated the population evolution of the B (B(t)), Qx (X(t)), and Qy (Y(t)) bands as shown in Fig. 5 by carrying out the NA-ESMD simulations. The B band in this population analysis is composed of excited states S3 − S10, the Qx band is S2, and the Qy band is S1. Population of each band at a given time was calculated as the average over all the trajectories. We assume a first-order irreversible transfer from B → Qx with a rate constant k1 and from Qx → Qy with a rate constant k2, yielding the sequential transfer pathway .


Non-radiative relaxation of photoexcited chlorophylls: theoretical and experimental study.

Bricker WP, Shenai PM, Ghosh A, Liu Z, Enriquez MG, Lambrev PH, Tan HS, Lo CS, Tretiak S, Fernandez-Alberti S, Zhao Y - Sci Rep (2015)

Averaged excited state populations of Qy (red), Qx (green), and B (blue) bands in (a) ChlA and (b) ChlB species during a 500 trajectory nonadiabatic excited-state molecular dynamics (NA-ESMD) simulation (Sim).Population model fit (first-order, irreversible) is also shown for Qy, Qx, and B bands (Fit). The excited state simulations were run for 1 ps, and began with an excitation pulse centered around the B band.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4561917&req=5

f5: Averaged excited state populations of Qy (red), Qx (green), and B (blue) bands in (a) ChlA and (b) ChlB species during a 500 trajectory nonadiabatic excited-state molecular dynamics (NA-ESMD) simulation (Sim).Population model fit (first-order, irreversible) is also shown for Qy, Qx, and B bands (Fit). The excited state simulations were run for 1 ps, and began with an excitation pulse centered around the B band.
Mentions: After initial excitation in the red edge of the B band of the two chlorophyll species, we calculated the population evolution of the B (B(t)), Qx (X(t)), and Qy (Y(t)) bands as shown in Fig. 5 by carrying out the NA-ESMD simulations. The B band in this population analysis is composed of excited states S3 − S10, the Qx band is S2, and the Qy band is S1. Population of each band at a given time was calculated as the average over all the trajectories. We assume a first-order irreversible transfer from B → Qx with a rate constant k1 and from Qx → Qy with a rate constant k2, yielding the sequential transfer pathway .

Bottom Line: Nonradiative relaxation of high-energy excited states to the lowest excited state in chlorophylls marks the first step in the process of photosynthesis.Modeling this process with non-adiabatic excited state molecular dynamics simulations uncovers a critical role played by the different side groups in the two molecules in governing the intramolecular redistribution of excited state wavefunction, leading, in turn, to different time-scales.This is achieved via selective participation of specific atomic groups and complex global migration of the wavefunction from the outer to inner ring, which may have important implications for biological light-harvesting function.

View Article: PubMed Central - PubMed

Affiliation: Department of Energy, Environmental and Chemical Engineering, Washington University, Saint Louis, Missouri 63130, USA.

ABSTRACT
Nonradiative relaxation of high-energy excited states to the lowest excited state in chlorophylls marks the first step in the process of photosynthesis. We perform ultrafast transient absorption spectroscopy measurements, that reveal this internal conversion dynamics to be slightly slower in chlorophyll B than in chlorophyll A. Modeling this process with non-adiabatic excited state molecular dynamics simulations uncovers a critical role played by the different side groups in the two molecules in governing the intramolecular redistribution of excited state wavefunction, leading, in turn, to different time-scales. Even given smaller electron-vibrational couplings compared to common organic conjugated chromophores, these molecules are able to efficiently dissipate about 1 eV of electronic energy into heat on the timescale of around 200 fs. This is achieved via selective participation of specific atomic groups and complex global migration of the wavefunction from the outer to inner ring, which may have important implications for biological light-harvesting function.

No MeSH data available.


Related in: MedlinePlus