We probe the local electronic structure at solvated Na+ ions in 1 M aqueous NaCl solutions as a
function of pH. A dramatic change in the Na+ white line intensity in x-ray absorption is observed
for high pH values, reflecting a changing local electronic structure at the Na+ ions when OH. is
present. Given the relative abundance of sodium and hydroxide ions, we conclude that one OH.
affects 2.4.0.6 Na+ ions in an electronically noticeable way at pH 13. From the experimental data
we infer that spatially extended clusters or networks incorporating Na+ and OH. can exist in the
electrolyte solution. The experimental data are complemented by molecular dynamics simulations,
which indicate the presence of structured clusters incorporating Na+, OH., and solvent molecules.