Low frequency Δν=0–350 cm−1, Raman intensity data were obtained from liquid water between 3.5 and 89.3 °C using holographic grating double and triple monochromators. The spectra were Bose–Einstein (BE) corrected, I/(1+n), and the total integrated (absolute) contour intensities were treated by an elaboration of the Young–Westerdahl (YW) thermodynamic method, assuming conservation of hydrogen‐bonded (HB) and nonhydrogen‐bonded (NHB=bent and/or stretched, O–H O) nearest‐neighbor O–O pairs. A ΔH°1 value of 2.6±0.1 kcal/mol O–H ⋅⋅⋅ O or 5.2±0.2 kcal/mol H2O (11 kJ/mol O–H ⋅⋅⋅ O, or 22 kJ/mol H2O) resulted for the HB→NHB process. This intermolecular value agrees quantitatively with Raman and infrared ΔH° values from the one‐ and two‐phonon OH‐stretching regions, and from molecular dynamics, depolarized light scattering, neutron scattering, and ultrasonic absorption, thus indicating a common process. A population involving partial covalency of, i.e., charge transfer into, the H ⋅⋅⋅ O units of linear and/or weak...

Temperature dependence of the low‐ and high‐frequency Raman scattering from liquid water

The Raman spectrum from water was obtained for a range of conditions from ambient to above the critical point, 256 bar and 400 °C. A fluorescence-free sapphire high-pressure Raman cell was employed with which the Raman spectra from water were examined between 30 and 4000 cm−1. Computer deconvolution of the Raman OH-stretching contours allowed the hydrogen bond strength to be determined from the integrated component intensity ratios by use of the van’t Hoff relationship. This procedure yielded a hydrogen bond enthalpy of 2.53±0.10 kcal/mol which is in excellent agreement with previously reported values.

Measurement of the Raman spectrum of liquid water

Precise isosbestic points occur in the Raman OH‐stretching spectra from liquid water between 3 and 85 °C if cell alignment is accomplished with Newton’s rings. Isosbestic frequencies measured for the orientations X(Y,X+Z)Y=6β2, X(ZX)Y=3β2, X(Y+Z,X+Z)Y=45α2+13β2, X(Z,X+Z)Y=45α2+7β2, and X(ZZ)Y=45α2+4β2 are 3524, 3522 (note β2 agreement), 3468, 3425, and 3403 cm−1, respectively. Isosbestic points from two different measurements calculated by the relations, X(ZZ)Y‐(4/3)X(ZX)Y and X(Z,X+Z)Y‐(7/6)X(Y,X+Z)Y agree exactly for 45α2, 3370 cm−1. (α and β2 correspond to the mean polarizability and square of the anisotropy.) The pure α2 isosbestic frequency, 3370 cm−1, coincides with the peak of the highest frequency hydrogen‐bonded (HB) Gaussian OH‐stretching component. The pure β2 isosbestic point, 3522–3524 cm−1, coincides with the peak of the nonhydrogen‐bonded (NHB) Gaussian OH‐stretching component, next above in frequency. The α2 and β2 isosbestic points are thus thought to provide an experimental distinction b...

Raman isosbestic points from liquid water

High-sensitivity fluorescence detector for fluorescein isothiocyanate derivatives of amino acids separated by capillary zone electrophoresis

In operando Raman investigation of Fe doping influence on catalytic NiO intermediates for enhanced overall water splitting

Weak, broad, Raman bands have been observed from water and heavy water at shifts above and below those corresponding to the intramolecular bending and stretching vibrations. Bands near Δv = 1190 cm−1 for D2O and Δv = 1625 cm−1 for H2O, in addition to relatively sharp bands at 1210 cm−1 for D2O and 1640 cm−1 for H2O are thought to arise from intramolecular bending vibrations of D2O and H2O molecules that are either partially, or fully hydrogen bonded. Other weak bands can be explained as combinations of known intra‐ and intermolecular vibrations, in particular, librations.

G. E. Walrafen

Papers

Weak Raman bands from water