Molecular and electronic structure in NaCl electrolytes of varying concentration: Identification of spectral fingerprints

Near edge x-ray absorption spectra at the Na K edge in aqueous NaCl electrolytes are presented as a function of concentration. The spectra are modeled by electronic structure calculations. We find and identify the orbital origin of two spectral fingerprints with sensitivity to the Na ⁺-H₂O distance and the Na⁺-Cl^- distance in the electrolyte. Interionic interaction is found to be crucial for the description of the electrolytes at high concentrations.