The Ag + state falls below 3Ag - at carotenoid-relevant conjugation lengths

Elliot J. Taffet, Gregory D. Scholes

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12 Scopus citations


Spectroscopy of all-trans linear polyenes is characterized by a one-photon electronic transition to a bright S2 state and two-photon transition to a lower-lying dark S1 state. We apply ab initio quantum chemistry to distinguish additional diffuse dark singlet states. Building on a systematic implementation of CASSCF and DMRGSCF coupled to strongly-contracted NEVPT2, we report the excitation energies for a series of polyenes from butadiene to C16H18 at optimized S0, S1 and S2 geometries. Ionic/covalent state inversion within each manifold is identified at seven conjugated double bonds, making the Bu - a dark intermediate state at its optimized geometry and the Ag + the S3 state at the S0 optimized geometry. The relevance of these results to the function of carotenoids in photosynthetic light harvesting is discussed.

Original languageEnglish (US)
Pages (from-to)757-767
Number of pages11
JournalChemical Physics
StatePublished - Nov 14 2018

All Science Journal Classification (ASJC) codes

  • General Physics and Astronomy
  • Physical and Theoretical Chemistry


  • Ab initio quantum chemistry
  • Complete active space
  • Density Matrix Renormalization Group
  • Multireference perturbation theory
  • N-Electron Valence Perturbation Theory
  • Static/dynamic correlation


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