%A Ming-Kang Brad Tsai %T THEORETICAL STUDY OF SOLVATION OF IONS BY ARGON ATOMS %X Gas phase experiments have been used to study the molecular properties of finite systems in order to minimize the environmental perturbations. The measurements conducted in vacuum environment setup the standard reference value of experimental observables which builds up the foundation of non-vacuum scientific researches. The solvents, e.g. noble gas atoms, used in the gas phase experiments play an important role, i.e. cooling down the system temperature in order to approach the 0?K and provide better spectroscopic measurement quality. The binding position of the solvent atoms also impacts the interpretation of the experimental results. The aid from the theoretical studies was limited due to the computational expense. Three projects are shown in this thesis to show the theoretical challenges in studying different complex systems. The first project is a model potential development with the inclusion of electron correlation at quantum chemistry level to study the (H2O)Arn- clusters. The second project is using the ab inito calculations to explain the infrared spectroscopic measurement of Mg+(H2O)Arn clusters. The last project is a study of the complex electronic structure of Fe+(H2O)Arn clustes with using state-of-the-art ab intio methods %D 2006 %K ab initio; drude model; solvation; argon; model potential %I University of Pittsburgh %L pittir9758