Fig. 3: Observation of a signature for ion pairing in the spectator ICD spectra at 349.4 eV (main 2p3/2 → 3d line, see Fig. 2) for several calcium salt solutions.
From: The solvation shell probed by resonant intermolecular Coulombic decay

In the top panel, CaCl2 solutions of different concentrations are explored. Concentrations lower than 1.5 M yield spectra similar to the 1.5 M one (see SI). In the bottom panel, 1.5 M Ca2+ solutions with different counter-ions are displayed. Details on the solution preparation [explaining, for instance, the Na+ contamination in the Ca(ClO)2 solution] are available in the “Methods” section.