“…SO 3 is considered to be one of the major pollutants − present in Earth’s atmosphere because of its role in the formation of atmospheric aerosols and its contributions toward acid rain via formation of sulfuric acid (SA), that is, H 2 SO 4 . − SO 3 is mainly formed in atmosphere by gas-phase oxidation of sulfur dioxide (SO 2 ). ,− In atmosphere, SO 3 rapidly reacts with water to form SA. SO 3 has drawn the attention of atmospheric chemists for a long time because of its pivotal role in the atmospheric acid rain and various nucleation processes. − Formation of SA through gas-phase hydrolysis of SO 3 has been extensively studied by various research groups, both experimentally ,− as well as theoretically. − Various investigations suggested that SA formation through the reaction between SO 3 and water monomer (WM) is unfavorable under atmospheric conditions because of high energy barrier (>28 kcal mol –1 ). − As a result, the effect of different catalysts, namely, water, ,− ,− ,− hydroperoxy radical, formic acid, , SA (as an auto catalyst), nitric acid, and ammonia (AM), on the hydrolysis of SO 3 , was studied by various research groups. Considering the combined effect of rate constants and catalysts’ concentrations, WM and AM were proposed to have significant contribution in total SA formation in the troposphere.…”