Theoretical Studies of Spectral Signatures of Large Amplitude Vibrational Motions

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Anne B. McCoy of the University of Washington is supported by an award from the Chemical Theory, Models and Computational Methods and the Chemical Structure, Dynamics and Mechanisms-A programs in the Division of Chemistry to develop theoretical and computational studies of the relationships between spectroscopic measurements of water and its structure and other properties. Despite its centrality to chemistry (and to life), there are many aspects of the structure and properties of water that scientists do not understand. Dr. McCoy's research focuses on small assemblies of water molecules, clusters, or water clusters that include an ion. By focusing on smaller assemblies, Dr. McCoy can perform detailed atomistic studies on the structures of the clusters and how they interact with light, which includes important quantum mechanical effects. Her work focuses on developing theoretical models and computational tools that enable such investigations. By working closely with experimental groups at Yale University, Pennsylvania State University and the University of Georgia, she is able to test her models. Along with her collaborators, Dr. McCoy is able to tease out insights into the structure and properties of these clusters from the available measurements. Dr. McCoy engages in activities that focus on development of the next generation of chemists. In addition to mentoring the students in her research group who come from diverse backgrounds, she has been a mentor to graduate students in each of the groups with whom her group collaborates. She also organizes several symposia, workshops or conferences each year, and uses these meetings as a forum to promote the development of early career scientists. In this work, Professor Anne McCoy is developing the theoretical and computational tools required to understand connections between the spectral features of large amplitude vibrational motions and the underlying inter- and intramolecular interactions, with a focus on water clusters and ion-doped water clusters. These are systems of considerable experimental interest, but the large amplitude motions make the interpretation of the spectra challenging. Dr. McCoy's work focuses on developing extensions to Diffusion Monte Carlo approaches to address challenges related to the difference in the time scales for the inter- and intramolecular motions. In addition, inspired by insights gained from the Diffusion Monte Carlo simulations, Dr. McCoy is developing and applying reduced dimensional approaches for interpreting vibrational spectra. A central theme of Dr. McCoy's work is in providing insights into the spectral consequences of large amplitude vibrational motions in water clusters as well as molecules, like the Criegee intermediate, the properties of which are of interest in modeling atmospheric processes.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.