Raman OD-Stretching Overtone Spectra from Liquid D₂O between 22 and 152 °C

Abstract

Raman OD-stretching (first) overtone spectra, X(Z,X+Z)Y, X(ZZ)Y, and X(ZX)Y, from pure D2O between 22 and 98 °C yield an isosbestic frequency near 5130 cm-1. This value corresponds to the X(ZX)Y fundamental isosbestic observed near 2624 cm-1, but not to the X(ZZ)Y fundamental isosbestic near 2429 cm-1, because the fundamental 2375 cm-1 correlated deuteron OD stretch, ν1, and its overtone, 2ν1, are weak in the X(ZX)Y spectra, compared to the three higher-frequency fundamentals, ν2, ν3, and ν4, and their overtones. The 2375 and 2475 cm-1 fundamentals and their overtones probably engage in coupling with a ≈175 cm-1 LA phonon which is supported by H-bonded aggregates or patches, whereas the corresponding data for H2O provide clear and unequivocal evidence for this LA coupling. Deconvolution of the X(Z,X+Z)Y overtone spectra, 22−152 °C, plus van't Hoff treatment yields an enthalpy for H bond, O−D···O, rupture of 2.8 ± 0.2 kcal/mol O−D···O, in good agreement with present values of 2.6 ± 0.2 and 2.8 ± 0.2 kcal/mol O−D···O, obtained from the fundamental X(ZZ)Y and X(ZX)Y spectra. Raman overtone measurements are important because the spacing between the four-Gaussian components is large in the overtone OD- and OH-stretching contours compared to the fundamentals.

Mass transfer in the Earth’s interior: fluid-melt interaction in aluminosilicate–C–O–H–N systems at high pressure and temperature under oxidizing conditions

“…5d), which is qualitatively similar to that reported for pure H 2 O as well as that of water in silicate-rich hydrous fluids and melts in silicate-H 2 O systems (Frantz et al 1993;Walrafen et al 1999;Foustoukos and Mysen 2015). This decrease is associated with diminishing asymmetry on the lowfrequency-side of the spectrum, a feature that has been ascribed to less influence of hydrogen bonding among water species with increasing temperature (Walrafen et al 1996(Walrafen et al , 1999Foustoukos and Mysen 2012). At all temperatures and pressures, the width of this band in spectra of hydrous melts is greater than in the spectra of silicate-bearing aqueous fluids.…”

Unified description of temperature-dependent hydrogen-bond rearrangements in liquid water

“…This measured isotope effect is consistent with the fact that the D 2 O HB is stronger than that for H 2 O, as evidenced by the difference in their enthalpies of vaporization (26). We note that our van't Hoff analysis of the Raman spectra is somewhat different from the more typical method employing Gaussian decomposition (8,27,28). Gaussian decomposition inherently assumes distinct populations of absorbers, but, given the results presented here, such an assumption is unjustified.…”

Local Dense Structural Heterogeneities in Liquid Water from Ambient to 300 MPa Pressure: Evidence for Multiple Liquid–Liquid Transitions

“…[38] This strange character of the "central" vibrational component was mentioned long ago, [30][31][32][33] but has not been discussed in much detail so far (although the definition of a "third state" has been suggested [31] ). We will now focus on the origin of this sub-band and its relation to the pressure-induced local structural changes in liquid water.…”