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Title: The role of high-level calculations in the assignment of the Q-band spectra of chlorophyll

We recently established a novel assignment of the visible absorption spectrum of chlorophyll-a that sees the two components Q{sub x} and Q{sub y} of the low-energy Q band as being intrinsically mixed by non-adiabatic coupling. This ended 50 years debate as to the nature of the Q bands, with prior discussion poised only in the language of the Born-Oppenheimer and Condon approximations. The new assignment presents significant ramifications for exciton transport and quantum coherence effects in photosystems. Results from state of the art electronic structure calculations have always been used to justify assignments, but quantitative inaccuracies and systematic failures have historically limited usefulness. We examine the role of CAM-B3LYP time-dependent density-functional theory (TD-DFT) and Symmetry Adapted Cluster-Configuration Interaction (SAC-CI) calculations in first showing that all previous assignments were untenable, in justifying the new assignment, in making some extraordinary predictions that were vindicated by the new assignment, and in then identifying small but significant anomalies in the extensive experimental data record.
Authors:
 [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [6]
  1. School of Physics and Materials Science, The University of Technology, Sydney NSW (Australia)
  2. School of Chemistry, Physics and Mechanical Engineering, Queensland University of Technology, Brisbane QLD4001 (Australia)
  3. Australian National University Supercomputer Facility, Mills Rd, Canberra, ACT 0200 (Australia)
  4. Institute of Physics, University of Tartu, Riia 142, 51014 Tartu (Estonia)
  5. Institute of Physics, University of Tartu, Riia 142, 51014 Tartu, Estonia and Institute of Molecular and Cell Biology, University of Tartu, Riia 23, 51010 Tartu (Estonia)
  6. Research School of Chemistry, The Australian National University, Canberra 2601 (Australia)
Publication Date:
OSTI Identifier:
22307926
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 1618; Journal Issue: 1; Conference: ICCMSE 2014: International conference on computational methods in science and engineering 2014, Athens (Greece), 4-7 Apr 2014; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ABSORPTION SPECTRA; ALLOCATIONS; BORN-OPPENHEIMER APPROXIMATION; CHLOROPHYLL; CONFIGURATION INTERACTION; COUPLING; DENSITY FUNCTIONAL METHOD; ELECTRONIC STRUCTURE; EXCITONS; SYMMETRY; TIME DEPENDENCE