Abstract
The role of the geometric phase effect in chemical reaction dynamics has long been a topic of active experimental and theoretical investigations. The topic has received renewed interest in recent years in cold and ultracold chemistry where it was shown to play a decisive role in state-to-state chemical dynamics. We provide a brief review of these developments focusing on recent studies of O + OH and hydrogen exchange in the H + H 2 and D + HD reactions at cold and ultracold temperatures. Non-adiabatic effects in ultracold chemical dynamics arising from the conical intersection between two electronic potential energy surfaces are also briefly discussed. By taking the hydrogen exchange reaction as an illustrative example it is shown that the inclusion of the geometric phase effect captures the essential features of non-adiabatic dynamics at collision energies below the conical intersection.
Highlights
Our description of chemical reactions largely relies on the Born–Oppenheimer (BO) approximation in which the fast-moving electronic degrees of freedom are separately treated from the slow moving nuclear coordinates which largely remain unchanged during an electronic transition
By taking the hydrogen exchange reaction as an illustrative example it is shown that the inclusion of the geometric phase effect captures the essential features of non-adiabatic dynamics at collision energies below the conical intersection
Althorpe and coworkers [24] have previously shown that the geometric phase (GP) and NGP scattering amplitudes can be rigorously expressed as a linear combination of the “direct” and “looping”
Summary
Our description of chemical reactions largely relies on the Born–Oppenheimer (BO) approximation in which the fast-moving electronic degrees of freedom are separately treated from the slow moving nuclear coordinates which largely remain unchanged during an electronic transition In this adiabatic approximation, the electronic problem is solved for different fixed nuclear configurations and the nuclei are assumed to evolve in a potential field created by the electrons. The electronic problem is solved for different fixed nuclear configurations and the nuclei are assumed to evolve in a potential field created by the electrons This separation is the basis of the vast majority of electronic structure and quantum dynamics studies and works amazingly well for many chemical reactions involving electronically ground state atoms and molecules. O + OH and the hydrogen exchange reactions as illustrative examples
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