Theoretical Studies Of Potential Energy Surfaces And Rovibrational Spectrum Of Rare Gas-carbon Disulfide Complexes:He-CS₂, Ne-CS₂and Ar-CS₂

Intermolecular interactions play an important role in many physical, chemical, and biological fields. Van der Waals complex is an ideal model in the research of intermolecular interactions. Such complexes have been extensively studied in both experiment and theory due to the remarkable development in high resolution spectroscopic techniques using supersonic expansion, as well as much availability of high-level ab initio calculations in large scale parallel computing environment. These studies have greatly enhanced our understanding on molecular interactions, or intermolecular potential energy. In the present dissertation, calculations were carried out to investigate the Rg-CS2(Rg=He, Ne, Ar) complexes systematically.Theoretical studies of the potential energy surfaces (PESs) and bound states are performed for rare gas-carbon disulfide complexes, He-CS2, Ne-CS2and Ar-CS2. We find that the three PESs have very similar features and each PES can be characterized by a global T-shaped minimum, two equivalent local linear minima and the saddle points between them. The T-shaped isomer is energetically more stable than the linear isomer for each complex. The linear isomers, which have not been observed in experiment so far, are predicted from our PES and further identified by bound state calculations. Moreover, we assign several intermolecular vibrational states for both the T-shaped and linear isomers of the three complexes via the analysis of wavefunctions. The corresponding vibrational frequencies are calculated from the bound state energies for these assigned states. These frequencies could be helpful for further spectroscopic studies in experiment, especially for the linear isomers. We also calculate the rovibrational transition frequencies for the three T-shaped isomers and the pure rotational transition frequencies for the linear isomers, respectively. The accuracy of the PESs is validated by the good agreement between theoretical and experimental results for the transition frequencies and spectroscopic parameters.