The Study of the Raman Band Shape of Sulfuric Acid and Proton Transfer

Abstract

Abstract The Raman bands of sulfuric acid and ammonium sulfate in aqueous solutions were observed in the S–O stretching region and were resolved into components with a Voigt profile. The concentration dependence of the half band-widths was examined. The 980 cm−1 band of SO42− in acidic solutions was determined to have a width of 8.0±0.3 cm−1 when unbroadened by any chemical process. In the concentration-half-width curve for this band, two conspicuous bends were found, at about 2 M and 8 M stoichiometric concentrations of H2SO4. It seems that the former bend is attributable to the disappearance of water clusters, and the latter, to the partial defect of the primary hydration shell of the oxonium ion. The interrelation between the half-widths of the 980 cm−1 and 1050 cm−1 bands suggests that the formation of the HSO4−·H3O+ ion pair is related to the spectroscopic lifetime of HSO4−.