Ion association dynamics in aqueous solutions of sulfate salts as studied by Raman band shape analysis - art. no. 034508

摘要

A new perspective is shown on the interaction between the sulfate ion and its counter cation in aqueous solutions. We propose the dynamic exchange model of ion association instead of the conventional static equilibrium model. The concentration dependence of the Raman band shape of the totally symmetric (a(1)) SO stretch mode of the sulfate ion is investigated systematically for four sulfate ions, MgSO4, (NH4)(2)SO4, K2SO4, and Li2SO4. The concentration dependence of the a(1) Raman band shape in the MgSO4 system is successfully reproduced by the analysis based on the dynamic exchange model. As a result, quantitative information about the extremely dynamic nature of the ion association has been obtained: the mean time between associations is a few picoseconds and the mean lifetime of association is several hundred femtoseconds. (c) 2005 American Institute of Physics.