Fig. 4: Determination of the valence-band spectrum of water molecules in the solvation shell of Ca2+.
From: The solvation shell probed by resonant intermolecular Coulombic decay
In the top panel, the valence-band region of the electron spectra off-resonance (at 346 eV) and on the main 2p3/2 → 3d resonance (at 349.4 eV) for the CaCl2 1.5 M solution are displayed. The valence band spectrum of pure water is also displayed for comparison. The different orbitals are attributed in the figure. The differences are attributed to the resonant participator ICD. The two spectra have been normalized so that the Cl 3p and 3s peaks overlap, as Cl− is not involved in participator ICD. In the bottom panel, the difference between the two spectra, corresponding to the participator ICD contribution only, is displayed along with a fit of the different peaks. This spectrum reflects the valence band of the Ca2+ solvation-shell water molecules. A contamination by Ca 2p photoionization with second-order light is notable in the 346 eV spectrum.
