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Download fileRotational Relaxation of Ionic Molecules in Electrolyte Solutions. Anisotropy Relaxation and Molecular Dynamics Study
journal contribution
posted on 1998-07-25, 00:00 authored by N. Balabai, M. G. Kurnikova, R. D. Coalson, D. H. WaldeckRotational diffusion of organic ions in electrolyte solution is studied via optically heterodyned
polarization spectroscopy and molecular dynamics (MD) simulations. Significant differences between the
behavior of organic cation and anion species were observed in the experiments. While the rotational relaxation
time of the anion normalized by the viscosity of the solution increases with the electrolyte concentration, the
normalized relaxation time of the cation decreases with increasing electrolyte concentration. The experimental
data are analyzed by using a continuum theory approach and MD simulations. It is demonstrated that one
must include ion pairs to describe the dynamics of the anion, but the analysis of the relaxation of the cation
does not require ion pairing. MD simulations show that the difference in the dynamics of the anion and
cation in electrolyte solution is caused by the different ability of free anion, free cation, and ion paired species
to associate with the solvent (DMSO).