Carotenoid Nuclear Reorganization and Interplay of Bright and Dark Excited States

Elliot J. Taffet, Benjamin G. Lee, Zi S.D. Toa, Natalie Pace, Garry Rumbles, June Southall, Richard J. Cogdell, Gregory D. Scholes

Research output: Contribution to journalArticlepeer-review

25 Scopus Citations

Abstract

We report quantum chemical calculations using multireference perturbation theory (MRPT) with the density matrix renormalization group (DMRG) plus photothermal deflection spectroscopy measurements to investigate the manifold of carotenoid excited states and establish their energies relative to the bright state (S2) as a function of nuclear reorganization. We conclude that the primary photophysics and function of carotenoids are determined by interplay of only the bright (S2) and lowest-energy dark (S1) states. The lowest-lying dark state, far from being energetically distinguishable from the lowest-lying bright state along the entire excited-state nuclear reorganization pathway, is instead computed to be either the second or first excited state depending on what equilibrium geometry is considered. This result suggests that, rather than there being a dark intermediate excited state bridging a non-negligible energy gap from the lowest-lying dark state to the lowest-lying bright state, there is in fact no appreciable energy gap to bridge following photoexcitation. Instead, excited-state nuclear reorganization constitutes the bridge from S2 to S1, in the sense that these two states attain energetic degeneracy along this pathway.

Original languageAmerican English
Pages (from-to)8628-8643
Number of pages16
JournalJournal of Physical Chemistry B
Volume123
Issue number41
DOIs
StatePublished - 17 Oct 2019

Bibliographical note

Publisher Copyright:
Copyright © 2019 American Chemical Society.

NREL Publication Number

  • NREL/JA-5900-75239

Keywords

  • carotenoid excited states
  • density matrix renormalization group
  • energies
  • multireference perturbation theory

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