THE STRUCTURAL AND DYNAMIC PROPERTIES OF SOME TRANSITION-METAL AQUA CATIONS - RESULTS FROM NEUTRON-SCATTERING

The following paper comprises a survey of the role neutron scattering methods have played to help understand the origins of the diverse prop erties of electrolyte solutions which contain transition metal cations . It is seen how neutron diffraction and isotopic substitution is able to resolve the local structure around contrasting ions, such as Cr3+, Ni2+, Fe3+, Fe2+, Cu2+, without recourse to sophisticated modelling p rocedures. Quasielastic neutron scattering (QNS) provides insight into the dynamics of the protons in solution. The results enable one to di stinguish between cations whose water molecules are coordinated on tim e scales larger than 5 x 10(-9) s, shorter than 10(-10) s, or intermed iate between those. two limits. QNS also provides information on the e xistence of a second relatively short-lived hydration shell distinct f rom the bulk water.