High Magnetic Field Detunes Vibronic Resonances in Photosynthetic Light Harvesting

Margherita Maiuri, Maria B. Oviedo, Jacob C. Dean, Michael Bishop, Bryan Kudisch, Zi S.D. Toa, Bryan M. Wong, Stephen A. McGill, Gregory D. Scholes

Research output: Contribution to journalArticlepeer-review

16 Scopus citations


The origin and role of oscillatory features detected in recent femtosecond spectroscopy experiments of photosynthetic complexes remain elusive. A key hypothesis underneath of these observations relies on electronic-vibrational resonance, where vibrational levels of an acceptor chromophore match the donor-acceptor electronic gap, accelerating the downhill energy transfer. Here we identify and detune such vibronic resonances using a high magnetic field that exclusively shifts molecular exciton states. We implemented ultrafast pump-probe spectroscopy into a specialized 25 T magnetic field facility and studied the light-harvesting complex PC645 from a cryptophyte algae where strongly coupled chromophores form molecular exciton states. We detected a change in high-frequency coherent oscillations when the field was engaged. Quantum chemical calculations coupled with a vibronic model explain the experiment as a magnetic field-induced shift of the exciton states, which in turn affects the electronic-vibrational resonance between pigments within the protein. Our results demonstrate the delicate sensitivity of interpigment coherent oscillations of vibronic origin to electronic-vibrational resonance interactions in light-harvesting complexes.

Original languageEnglish (US)
Pages (from-to)5548-5554
Number of pages7
JournalJournal of Physical Chemistry Letters
Issue number18
StatePublished - Sep 20 2018

All Science Journal Classification (ASJC) codes

  • Materials Science(all)
  • Physical and Theoretical Chemistry


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