Sarah Hall
Speaker's Institution
Colorado State University
Chemistry A101
Mixer Time
Mixer Location
Chemistry B101E
Additional Information

About the Seminar

Conical intersections are seams between two potential energy surfaces, at which the degeneracy allows for ultrafast decay to a lower energy state. This connection between potential energy surfaces is present in many photochemical reactions, such as the photoisomerization of rhodopsin that is responsible for the initiation of the visual signaling process.1 Because these reactions occur on sub-picosecond timescales, ultrafast spectroscopy is one method that has been used to study systems with conical intersections.1 In a recent collaboration between the Fleming and Head-Gordon groups at the University of California, Berkeley, the researchers used two-dimensional electronic-vibrational (2DEV) spectroscopy and electronic structure calculations to study crystal violet and malachite green, two phenylmethane dyes that are known to experience relaxation through conical intersections.2 2DEV spectroscopy provides information about coupling between electronic and vibrational transitions, as well as improved resolution of peaks in 2D spectra compared to other 2D spectroscopy techniques.3 By combining experimental and computational methods, the researchers were able to match features of the 2DEV spectra to the geometries of the dyes at different points along their potential energy surfaces, showing the complete pathway from photoexcitation to relaxation through a conical intersection. Their work demonstrates the ability of 2DEV spectroscopy to provide information about reactions with electronic-vibrational coupling, and offers a comprehensive method for the study of conical intersections.


  1. Polli, D. et al.Tracking the primary photoconversion events in rhodopsins by ultrafast optical spectroscopy. Photochem Photobiol Sci14, 213–228 (2015).
  2. Wu, E. et al. Two-dimensional electronic-vibrational spectroscopic study of conical intersection dynamics: an experimental and electronic structure study. Phys. Chem. Chem. Phys. 21, 14153-14163 (2019).
  3. Oliver, T., Lewis, N., Fleming, G. Correlating the motion of electrons and nuclei with two-dimensional electronic–vibrational spectroscopy. Proc Natl Acad Sci USA 111, 10061-10066 (2014).