TY - JOUR
T1 - Experimental Detection of Branching at a Conical Intersection in a Highly Fluorescent Molecule
AU - Brazard, Johanna
AU - Bizimana, Laurie A.
AU - Gellen, Tobias
AU - Carbery, William P.
AU - Turner, Daniel B.
N1 - Publisher Copyright:
© 2015 American Chemical Society.
PY - 2016/1/7
Y1 - 2016/1/7
N2 - 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.
AB - 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.
KW - conical intersection
KW - femtosecond transient absorption
KW - oxazine molecules
KW - surface crossing
KW - vibrational wavepacket
UR - http://www.scopus.com/inward/record.url?scp=84954042936&partnerID=8YFLogxK
U2 - 10.1021/acs.jpclett.5b02476
DO - 10.1021/acs.jpclett.5b02476
M3 - Article
AN - SCOPUS:84954042936
VL - 7
SP - 14
EP - 19
JO - Journal of Physical Chemistry Letters
JF - Journal of Physical Chemistry Letters
IS - 1
ER -