Conical intersections, due to their ubiquity in larger molecules, their key role in nonradiative relaxation following photoexcitation and, in some cases, their role in thermal isomerization, have a significant impact on the dynamics of molecules ranging from photoswitches to DNA nucleobases. The nonadiabatic behavior around conical intersections in solution, both in thermal equilibrium and following vertical excitation, is a matter of great interest as understanding this behavior would open avenues toward engineering molecules with favorable photoyields and thermal isomerization rates. Methods of study for conical intersections in solution must be carefully selected to address both dissipation and nonadiabatic effects due to strong coupling between electronic and vibrational degrees of freedom. In the interest of studying how thermal and vertical behaviors around a conical intersection are affected by the diabatic coupling strength, we carried out quantum jump dynamics on a two mode, double-well structured conical intersection model. The jump probabilities between eigenstates were organized into a Markov state model to which we applied transition path theory. Transition path theory, a method frequently used to find reaction rates and pathways in complex systems, produced committor probabilities for each eigenstate in the system as well as thermal barrier crossing rates and principal pathways that we interrogated for mechanistic information. We characterized the nature of the transition path ensemble in the thermal case, finding tunneling dominated pathways at low diabatic coupling and transitions states of mixed diabatic state character dominated at high diabatic coupling. We employed a similar method to extract yields and important relaxation pathways from the evolution of vertically excited trajectories. Analysis of common pathways rationalized the increase in photoyield and thermal barrier crossing rate with diabatic coupling strength.

Elucidating conical intersection dynamics in solution with quantum jumps and Markov state models

Fall 2022 abstracts, posters, and presentations will launch in mid-September.

ACS Fall 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.