7. Speciation in aqueous solution

EXAFS is an ideal technique for determining the coordination polyhedron of ions in solution. The example presented here concerns concentrated solutions of pentavalent neptunium, in which Np-Np interaction is possible. To understand the mechanisms by which such complexes are formed in solution, it is necessary to know their structure. Raman scattering and X-ray diffraction experiments have suggested the existence of two structural forms, one (I) with one bond between the axial oxygen of one ${\mathrm{NpO}}_2^{+}$ and the neptunium of the other ${\mathrm{NpO}}_2^{+}$ cation, and...