Ultrafast structural dynamics of UV photoexcited cis,cis-1,3-cyclooctadiene observed with time-resolved electron diffraction

Abstract

Conjugated diene molecules are highly reactive upon photoexcitation and can relax through multiple reaction channels that depend on the position of the double bonds and the degree of molecular rigidity. Understanding the photoinduced dynamics of these molecules is crucial for establishing general rules governing the relaxation and product formation. Here, we investigate the femtosecond time-resolved photoinduced excited-state structural dynamics of cis,cis-1,3-cyclooctadiene, a large-flexible cyclic conjugated diene molecule, upon excitation with 200 nm using mega-electron-volt ultrafast electron diffraction and trajectory surface hopping dynamics simulations. We tracked the photoinduced structural changes from the Franck–Condon region through the conical intersection seam to the ground state. Our findings revealed a novel primary reaction coordinate involving ring distortion, where the ring stretches along one axis and compresses along the perpendicular axis. The nuclear wavepacket remains compact along this reaction coordinate until it reaches the conical intersection seam, and it rapidly spreads as it approaches the ground state, where multiple products are formed.

Publication
Phys. Chem. Chem. Phys.
Yusong Liu
Yusong Liu
Associate Staff Scientist
Surjendu Bhattacharyya
Surjendu Bhattacharyya
Postdoctoral Researcher
Elio Champenois
Elio Champenois
Sr. Staff Systems Scientist, ASML
Matt Ware
Matt Ware
Staff Scientist, SRI International
Thomas Wolf
Thomas Wolf
Staff Scientist

My research is focused on discovering structure-function relationships in ultrafast photochemistry to better understand and eventually control this type of reactions.