This project in the Theoretical and Computational Chemistry Program concerns the study of certain fundamental processes affecting chemical reactions. In particular, new algorithms will be developed and tested to calculate phenomena that couple the detailed motions of electrons and nuclei. Such interactions are often neglected, but can have important effects that are only beginning to be understood. Applications will be made to several problems of current experimental interest, including the spectra of lithium hydride and nitrogen molecules, the quenching of electronically excited sodium atoms, and charge transfer reactions.