Vibronic Conical\nIntersection Trajectory Signatures\nin Wave Packet Coherences

Conical intersections are ubiquitous in the energy landscape\nof\nchemical systems, drive photochemical reactivity, and are extremely\nchallenging to observe spectroscopically. Using two-dimensional electronic\nspectroscopy, we observe the nonadiabatic dynamics in Wurster’s\nBlue after excitation to the lowest two vibronic excited states. The\nexcited populations relax ballistically through a conical intersection\nin 55 fs to the electronic ground state potential energy surface as\nthe molecule undergoes an intramolecular electron transfer. While\nthe kinetics are identical on both vibronic energy surfaces, we observe\ndifferent patterns of coherent oscillations after traversing the conical\nintersection indicating distinct nonadiabatic relaxation pathways\nthrough the conical energetic funnel. These coherences are not created\ndirectly by the excitation pulses but are the result of the dynamical\ntrajectories projecting differently on the conical intersection vibrational\nspace. Our spectroscopic data offers a fresh perspective into the\ncomplex conical intersection topology and dynamics that emphasizes\nthe critical involvement of the intersection space in dictating the\ndynamics.