Non-radiative relaxation of photoexcited chlorophylls: theoretical and experimental study.
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.
Department of Energy, Environmental and Chemical Engineering, Washington University, Saint Louis, Missouri 63130, USA.
William P
WP
Bricker
Division of Materials Science, Nanyang Technological University, Singapore 639798.
Prathamesh M
PM
Shenai
Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371.
Avishek
A
Ghosh
Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371.
Zhengtang
Z
Liu
Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371.
Miriam Grace M
MG
Enriquez
Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371.|Biological Research Center, Hungarian Academy of Sciences, 6726 Szeged, Temesvari krt. 62, Hungary.
Petar H
PH
Lambrev
Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371.
Howe-Siang
HS
Tan
Department of Energy, Environmental and Chemical Engineering, Washington University, Saint Louis, Missouri 63130, USA.
Cynthia S
CS
Lo
Theoretical Division, Center for Nonlinear Studies (CNLS), and Center for Integrated Nanotechnologies (CINT), Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
Sergei
S
Tretiak
Universidad Nacional de Quilmes, Roque Saenz Pea 352, B1876BXD Bernal, Argentina.
Sebastian
S
Fernandez-Alberti
Division of Materials Science, Nanyang Technological University, Singapore 639798.
Yang
Y
Zhao
D002734:Chlorophyll / Q000096:biosynthesis* / Q000737:chemistry; D000077194:Chlorophyll A; D008027:Light; D008962:Models, Theoretical; D010788:Photosynthesis; D013057:Spectrum Analysis
D002734:Chlorophyll; C037184:chlorophyll b; D000077194:Chlorophyll A