UC Berkeley

Understanding reaction dynamics in chemical systems is the first step towards manipulating those reactions to improve efficiency or avoid undesired products. Computational modeling plays a central role in the understanding of reaction dynamics, with that role ever increasing as computational power grows. Such modeling remains challenging, however. Studying reaction mechanisms in classical systems often proves extremely complicated due to the rare nature of reactive events and the many degrees of freedom that are involved. Classical reactions in solution are complicated further by the interactions of the system with the solvent degrees of freedom. The study of reaction mechanisms becomes more complicated still in quantum systems, where confounding behaviors such as interference and tunneling may occur.

Many powerful methods for understanding classical reaction mechanisms, adept at circumventing the problems posed by many degrees of freedom and rare events, have been developed, including transition path theory. Transition path theory is a method built on the committor, the probability for a reaction to occur, which defines a perfect reaction coordinate and the transition state. In this thesis we employ the Redfield quantum master equations to extend transition path theory to address the problems in common between classical and quantum reaction mechanism studies as well as those unique to quantum reactions. We extend this quantum transition path theory to address systems in and out of equilibrium, then derive a general quantum committor which is applicable to the study of systems in which the assumptions underlying quantum transition path theory do not apply, allowing us to quantify the impact of coherent effects on quantum reactions and propose means for coherent quantum control.