Extended X-Ray-Absorbtion Fine-Structure Studies of Local Ordering in Highly Concentrated Aqueous Solutions of CuBr2

EXAFS (extended x-ray-absorption fine structure) spectra of Cu${\mathrm{Br}}_2$ aqueous solutions at various concentrations have been analyzed both for Br and Cu $K$ edges. They show a local ordering of the Cu and Br ions in planar structure which spreads as the concentration is increased up to saturation. Our data give a direct confirmation of the local-ordering model proposed recently on the basis of Raman and viscosity measurements.