The study of hydration effects in aqueous solutions of LiCl and CsCl by inelastic neutron scattering

Data analysis of inelastic neutron scattering experiments in 2.14M aqueous LiCl and CsCl solutions is presented. The diffusion parameters of hydration water molecules (residence time, diffusion coefficients) were extracted fr om the quasi-elastic component of the scattering law S(Q,omega). It was est ablished that there are about four molecules in the hydration shell of a Li + ion, and their diffusion mobility is strongly hampered. A Cs+ ion has abo ut 8 molecules in its hydration shell, and this ion intensifies the diffusi on motion of surrounding molecules. The dynamic hydration numbers were esti mated: 3.7 for a Li+ ion and similar to 1 for a Cs+ ion. The generalized fr equency distributions for water molecules hydrating Li+ and Cs+ ions were o btained from the inelastic part of S(Q,omega). The effects observed indicat e essential distortion of the hydrogen-bond (H-B) network in the vicinity o f both ions, but the character of this distortion has different physical na tures. (C) 1999 Elsevier Science B.V. All rights reserved.