Stretching Band Of Water Research Articles

Effects of Ions on the OH Stretching Band of Water as Revealed by ATR-IR Spectroscopy

The effects of various cations (Li+, Na+, K+, Rb+, Cs+, Mg2+, Ca2+, Sr2+, Ba2+, Mn2+, Co2+, and Ni2+) and anions (Cl−, Br−, I−, $$ {\text{NO}}_{3}^{ - } $$ , $$ {\text{ClO}}_{4}^{ - } $$ , $$ {\text{HCO}}_{3}^{ - } $$ , and $$ {\text{CO}}_{3}^{2 - } $$ ) on the molar absorptivity of water in the OH stretching band region (2,600–3,800 cm−1) were ascertained from attenuated total reflection infrared spectra of aqueous electrolyte solutions (22 in all). The OH stretching band mainly changes linearly with ion concentrations up to 2 mol·L−1, but several specific combinations of cations and anions (Cs2SO4, Li2SO4, and MgSO4) present different trends. That deviation is attributed to ion pair formation and cooperativity in ion hydration, which indicates that the extent of the ion–water interaction reflected by the OH stretching band of water is beyond the first solvation shell of water molecules directly surrounding the ion. The obtained dataset was then correlated with several quantitative parameters representing structural and dynamic properties of water molecules around ions: ΔG HB, the structural entropy (S str), the viscosity B-coefficient (B η ), and the ionic B-coefficient of NMR relaxation (B NMR). Results show that modification of the OH stretching band of water caused by ions has quasi-linear relations with all of these parameters. Vibrational spectroscopy can be a useful means for evaluating ion–water interaction in aqueous solutions.

Raman Study of the Influence of KCl and KI on Polarization Contours of OH Stretching Band of Water

Raman Study of the Influence of KCl and KI on Polarization Contours of OH Stretching Band of Water

Raman Study of the Influence of KCl and KI on Polarization Contours of OH Stretching Band of Water

Changes in the isotropic and anisotropic contours of H2O stretching bands in solutions of KCl and KI were studied. The change of the isotropic contour of the OH stretching band in aqueous KCl solutions involves two parameters: the non-coincidence parameter, Δν and the Fermi resonance coupling constant, W. For KI solutions an additional change is caused by an increase in the distance between unperturbed ν1 and 2ν2. The non-coincidence parameter Δν decreases and changes its sign for the molar ratio of about 0.1 and the Fermi resonance constant W also decreases, when the electrolyte concentration increases.