In this project in the Theoretical and Computational Program of the Chemistry Division, Professor Sibert will carry out a set of fully quantum mechanical calculations of rotation-vibration states of polyatomic molecules. A knowledge of these states is necessary to predict the rates of chemical reactions. The calculations will encompass a wide range of molecules using both variational and perturbative techniques. The goal of the calculations is to elucidate the connections between Born-Oppenheimer potential energy surfaces and the dynamics and spectroscopy, which occurs as a result of motion on these surfaces. The systems to be treated will include H2O, SO2, HCN, HCCH, NH3, and H2CO. Coordinate and basis set representations will be developed which facilitate not only the calculation of spectra given a potential energy surface, but also the inverse, namely, the calculation of potential energy surfaces given the spectra. The representation chosen to describe the rotating-vibrating molecules will be specifically designed to describe certain large amplitude motions for which Jacobi coordinates are inadequate. An understanding of these transformations plays a pivotal role in our ability to understand and develop theories of reaction rates, reaction dynamics, collisional energy transfer, and mode specific effects.
