title: Challenges facing an understanding of the nature of low-energy excited states in photosynthesis.
abstract: While the majority of the photochemical states and pathways related to the biological capture of solar energy are now well understood and provide paradigms for artificial device design, additional low-energy states have been discovered in many systems with obscure origins and significance. However, as low-energy states are naively expected to be critical to function, these observations pose important challenges. A review of known properties of low energy states covering eight photochemical systems, and options for their interpretation, are presented. A concerted experimental and theoretical research strategy is suggested and outlined, this being aimed at providing a fully comprehensive understanding.
authors.affiliation: International Centre for Quantum and Molecular Structures, College of Sciences, Shanghai University, Shanghai 200444, China; School of Mathematical and Physical Sciences, The University of Technology Sydney, Sydney, NSW 2007, Australia. Electronic address: jeffrey.reimers@uts.edu.au.
authors.forename: Jeffrey R
authors.initials: JR
authors.lastname: Reimers
authors.affiliation: International Centre for Quantum and Molecular Structures, College of Sciences, Shanghai University, Shanghai 200444, China.
authors.forename: Malgorzata
authors.initials: M
authors.lastname: Biczysko
authors.affiliation: Department of Biological Sciences, Brock University, St. Catharines, ON, Canada.
authors.forename: Douglas
authors.initials: D
authors.lastname: Bruce
authors.affiliation: Department of Chemistry, Boston University, 590 Commonwealth Avenue, Boston, MA 02215, USA.
authors.forename: David F
authors.initials: DF
authors.lastname: Coker
authors.affiliation: School of Physical, Environmental and Mathematic Sciences, The University of New South Wales Canberra ACT 2600, Australia.
authors.forename: Terry J
authors.initials: TJ
authors.lastname: Frankcombe
authors.affiliation: Department of Applied Chemistry for Environment, School of Science and Technology, Kwansei Gakuin University, 2-1 Gakuen, Sanda, Hyogo 669-1337, Japan.
authors.forename: Hideki
authors.initials: H
authors.lastname: Hashimoto
authors.affiliation: Photonics Institute, TU Wien, Gusshausstrasse 27, 1040 Vienna, Austria.
authors.forename: Jürgen
authors.initials: J
authors.lastname: Hauer
authors.affiliation: Department of Chemistry and Department of Physics, Kansas State University, Manhattan, KS 66505, USA.
authors.forename: Ryszard
authors.initials: R
authors.lastname: Jankowiak
authors.affiliation: Zuse-Institute Berlin, Takustr. 7, 14195 Berlin, Germany.
authors.forename: Tobias
authors.initials: T
authors.lastname: Kramer
authors.affiliation: Institute of Physics, University of Tartu, Ravila 14c, 50411 Tartu, Estonia.
authors.forename: Juha
authors.initials: J
authors.lastname: Linnanto
authors.affiliation: Department of Chemistry, Ångström Laboratory, Uppsala University, Uppsala, Sweden.
authors.forename: Fikret
authors.initials: F
authors.lastname: Mamedov
authors.affiliation: Institute of Theoretical Physics, Johannes Kepler University Linz, Altenberger Str. 69, 4040 Linz, Austria.
authors.forename: Frank
authors.initials: F
authors.lastname: Müh
authors.affiliation: Institute of Physics, University of Tartu, Ravila 14c, 50411 Tartu, Estonia.
authors.forename: Margus
authors.initials: M
authors.lastname: Rätsep
authors.affiliation: Institute of Theoretical Physics, Johannes Kepler University Linz, Altenberger Str. 69, 4040 Linz, Austria.
authors.forename: Thomas
authors.initials: T
authors.lastname: Renger
authors.affiliation: Department of Chemistry, Ångström Laboratory, Uppsala University, Uppsala, Sweden.
authors.forename: Stenbjörn
authors.initials: S
authors.lastname: Styring
authors.affiliation: Key Laboratory of Pesticide & Chemical Biology (CCNU), Ministry of Education, College of Chemistry, Central China Normal University, Wuhan 430079, China.
authors.forename: Jian
authors.initials: J
authors.lastname: Wan
authors.affiliation: Laboratory of Soft Matter Physics, Institute of Physics, Chinese Academy of Sciences (CAS), Beijing 100190, China.
authors.forename: Zhuan
authors.initials: Z
authors.lastname: Wang
authors.affiliation: Faculty of Science, Ibaraki University, Mito 310-8512, Japan.
authors.forename: Zheng-Yu
authors.initials: ZY
authors.lastname: Wang-Otomo
authors.affiliation: Laboratory of Soft Matter Physics, Institute of Physics, Chinese Academy of Sciences (CAS), Beijing 100190, China.
authors.forename: Yu-Xiang
authors.initials: YX
authors.lastname: Weng
authors.affiliation: Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Nanxincun 20, Xiangshan, Beijing 100093, China.
authors.forename: Chunhong
authors.initials: C
authors.lastname: Yang
authors.affiliation: Department of Chemistry, Renmin University of, China.
authors.forename: Jian-Ping
authors.initials: JP
authors.lastname: Zhang
authors.affiliation: Institute of Physics, University of Tartu, Ravila 14c, 50411 Tartu, Estonia; Institute of Molecular and Cell Biology, University of Tartu, Riia 23, 51010 Tartu, Estonia. Electronic address: arvi.freiberg@ut.ee.
authors.forename: Arvi
authors.initials: A
authors.lastname: Freiberg
authors.affiliation: Research School of Chemistry, The Australian National University, Canberra, ACT 0200, Australia. Electronic address: krausz@rsc.anu.edu.au.
authors.forename: Elmars
authors.initials: E
authors.lastname: Krausz
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry; D045342:Light-Harvesting Protein Complexes / Q000737:chemistry; D010788:Photosynthesis; D045331:Photosystem I Protein Complex / Q000737:chemistry; D045332:Photosystem II Protein Complex / Q000737:chemistry; D045524:Phycobilisomes / Q000737:chemistry
chemical_list: D001426:Bacterial Proteins; C086320:FMO bacteriochlorophyll protein, Bacteria; D045342:Light-Harvesting Protein Complexes; D045331:Photosystem I Protein Complex; D045332:Photosystem II Protein Complex; D045524:Phycobilisomes
keywords: Charge transfer; Excited states; Exciton coupling; Non-photochemical quenching; Photosynthesis; Primary charge separation