title: Separating annihilation and excitation energy transfer dynamics in light harvesting systems.
abstract: The dependence of excitation energy transfer kinetics on the electronic state of the acceptor (ground vs excited) has been resolved with a novel multipulse prePump-Pump-Probe spectroscopy. The primary energy transfer and annihilation dynamics in two model light-harvesting systems were explored: an artificially synthesized carotenoid-zinc-phthalocyanine dyad and a naturally occurring light-harvesting peridinin-chlorophyll protein complex from Amphidinium carterae. Both systems use carotenoid as the primary excitation energy donor with porphyrin chromophores as the acceptor molecules. The prePump-Pump-Probe transient signals were analyzed with Monte Carlo modeling to explicitly address the underlying step-by-step kinetics involved in both excitation migration and annihilation processes. Both energy transfer and annihilation dynamics were demonstrated to occur with approximately the same rate in both systems, regardless of the excitation status of the acceptor pigments. The possible reasons for these observations are discussed in the framework of the Förster energy transfer model.
authors.affiliation: Quantum Electronics Department, Faculty of Physics, Vilnius University , Saulėtekio 9-III, 10222 Vilnius, Lithuania.
authors.forename: Mikas
authors.initials: M
authors.lastname: Vengris
authors.forename: Delmar S
authors.initials: DS
authors.lastname: Larsen
authors.forename: Leonas
authors.initials: L
authors.lastname: Valkunas
authors.forename: Gerdenis
authors.initials: G
authors.lastname: Kodis
authors.forename: Christian
authors.initials: C
authors.lastname: Herrero
authors.forename: Devens
authors.initials: D
authors.lastname: Gust
authors.forename: Thomas
authors.initials: T
authors.lastname: Moore
authors.forename: Ana
authors.initials: A
authors.lastname: Moore
authors.forename: Rienk
authors.initials: R
authors.lastname: van Grondelle