Two-dimensional spectroscopy of a molecular dimer unveils the effects of vibronic coupling on exciton coherences

Alexei Halpin, Philip J.M. Johnson, Roel Tempelaar, R. Scott Murphy, Jasper Knoester, Thomas L.C. Jansen, R. J.Dwayne Miller

Research output: Contribution to journalArticlepeer-review

150 Scopus citations

Abstract

The observation of persistent oscillatory signals in multidimensional spectra of protein-pigment complexes has spurred a debate on the role of coherence-assisted electronic energy transfer as a key operating principle in photosynthesis. Vibronic coupling has recently been proposed as an explanation for the long lifetime of the observed spectral beatings. However, photosynthetic systems are inherently complicated, and tractable studies on simple molecular compounds are needed to fully understand the underlying physics. In this work, we present measurements and calculations on a solvated molecular homodimer with clearly resolvable oscillations in the corresponding two-dimensional spectra. Through analysis of the various contributions to the nonlinear response, we succeed in isolating the signal due to inter-exciton coherence. We find that although calculations predict a prolongation of this coherence due to vibronic coupling, the combination of dynamic disorder and vibrational relaxation leads to a coherence decay on a timescale comparable to the electronic dephasing time.

Original languageEnglish (US)
Pages (from-to)196-201
Number of pages6
JournalNature chemistry
Volume6
Issue number3
DOIs
StatePublished - Mar 1 2014

ASJC Scopus subject areas

  • Chemistry(all)
  • Chemical Engineering(all)

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