Atmospheric aerosols impact the Earth-atmosphere system in several aspects.The effects of aerosols have been received extensive attention.However,the formation of atmospheric aerosol from microscopic aspect remains limited.Ionic & molecular(including hydrated)cluster with molecular specificity,selected sizes,and controlled compositions are ideal model systems to understand condensed phases processes and obtain molecular-level understanding of environmental materials and solution chemistry.In our study,we used the Low-Temperature Anion Photoelectron Spectroscopy and Atmospheric Pressure Inlet Time-of-Flight Mass Spectroscopy to study the alkali-halide clusters,halogen higher oxides: XOn.and stepwise of hydration of IO3-.In theoretical study,we used the Basin-Hopping/Genetic Algorithm for global minimum search and DFT/ab initio calculations for Local optimization.