Nonadiabatic and quantum effects in chemical dynamics

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Millard Alexander is supported by an award from the Chemical Theory, Models and Computational Methods program in the chemistry division to use quantum mechanics to investigate how chemical reactions involving molecular free radicals occur on multiple potential energy surfaces (PES's), with a particular focus on elementary reactions of wide experimental interest. The unique methodology developed by Alexander and coworkers is crucial for interpreting and challenging ongoing experimental investigations. These methods provide one of the most advantageous ways to carry out highly accurate state-to-state calculations on the dynamics of chemical reactions involving multiple PES's. Alexander is extending this approach to simulate the dynamics of more complex open-shell systems and also developing novel quantum mechanical finite-element based approaches to treat the collision dynamics and visualize the results, portraying the spatial behavior of the wavefunctions for reactive collisions and the spatial evolution of the quantum analogue of how a chemical reaction "flows" over a potential energy surface. Another research project focuses on how temporary trapping of collision partners manifests itself in quantum ?resonances?, which can be probed by novel experiments involving collisions of cold atoms. Molecular free radicals play a key role in many chemical environments, including combustion, propulsion, materials processing, plasmas, and remediation chemistry. Alexander's research provides a foundation for understanding the results of recent experiments, as well as important chemical processes in the atmosphere, interstellar gas clouds and cold chemistry. The Alexander group freely distributes computer codes and advanced instructional modules in collision dynamics and quantum chemistry.