Experimental Detection of Branching at a Conical Intersection in a Highly Fluorescent Molecule

Johanna Brazard, Laurie A. Bizimana, Tobias Gellen, William P. Carbery, Daniel B. Turner

Research output: Contribution to journalArticlepeer-review


Conical intersections are molecular configurations at which adiabatic potential-energy surfaces touch. They are predicted to be ubiquitous, yet condensed-phase experiments have focused on the few systems with clear spectroscopic signatures of negligible fluorescence, high photoactivity, or femtosecond electronic kinetics. Although rare, these signatures have become diagnostic for conical intersections. Here we detect a coherent surface-crossing event nearly two picoseconds after optical excitation in a highly fluorescent molecule that has no photoactivity and nanosecond electronic kinetics. Time-frequency analysis of high-sensitivity measurements acquired using sub-8 fs pulses reveals phase shifts of the signal due to branching of the wavepacket through a conical intersection. The time-frequency analysis methodology demonstrated here on a model compound will enable studies of conical intersections in molecules that do not exhibit their diagnostic signatures. Improving the ability to detect conical intersections will enrich the understanding of their mechanistic role in molecular photochemistry.

Original languageEnglish (US)
Pages (from-to)14-19
Number of pages6
JournalJournal of Physical Chemistry Letters
Issue number1
StatePublished - Jan 7 2016


  • conical intersection
  • femtosecond transient absorption
  • oxazine molecules
  • surface crossing
  • vibrational wavepacket

ASJC Scopus subject areas

  • General Materials Science
  • Physical and Theoretical Chemistry


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