Special P.Chem & AMO Physics Seminar: Prof. Hua Guo

Wed, Nov 14 3:00pm
Young Hall 2033
Speaker Hua Guo
University of New Mexico
Department of Chemistry and Chemical Biology

Phase or Faith: The Molecular Aharanov-Bohm Effect in Unimolecular Reactions

It is a standard practice in chemistry to consider reaction dynamics as nuclear motion on an adiabatic potential energy surface based on the Born-Oppenheimer approximation. This approximation, which forms a cornerstone of modern chemistry, rests on the large disparity between electronic and nuclear masses. However, it also engenders a geometric phase in electronic wavefunction when encircling a conical intersection. While non-adiabatic transitions are known to occur between different adiabatic states near a conical intersection in such processes as internal conversion, it is still commonly believed that the adiabatic dynamics can be reasonably approximated by this single-state adiabatic model. We demonstrate that adiabatic dynamics of photodissociation and unimolecular reactions can be strongly influenced by the geometric phase associated with a conical intersection along the reaction pathway, even when the energy is much lower than the crossing point. This so-called molecular Aharonov-Bohm effect can be thought as a quantum interference, which can significantly affect not only the tunneling lifetimes, but also product state distributions. These results suggest important caveats to adiabatic treatments of reaction dynamics.