Ludwik Adamowicz of the University of Arizona is supported by an award from the Theoretical and Computational Chemistry program within the Division of Chemistry for research on the development and implementation of methods for carrying out direct, rigorous, variational non-Born-Oppenheimer (non-BO) calculations for H3+ and its isotopomers using explicitly correlated multi-particle Gaussian basis functions (ECGs). The project has two main foci. The first is the formal development of the theoretical model for non-BO calculations of three-nucleus molecular systems and the computational implementation of the theory. The second is the application of the method to study the rovibrational spectra of H3+ and its isotopomers. The proposed approach is the first to describe triatomic systems in excited rovibrational states in a non-BO context. Broader impacts of the project include the elevation of the predictive capabilities of molecular quantum mechanics in describing rovibrational properties of triatomic systems. The new capabilities which will result will allow, for the first time, consideration of chemical reaction processes without the confines of the BO approximation and are expected to have a broad impact on all of Chemistry.
