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

Abstract

Low frequency Δν̄=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 weakly bent hydrogen bonds, O–H ⋅⋅⋅ O; is transformed into a second high energy population involving bent, e.g., 150° or less, and/or stretched, e.g., 3.2 Å, but otherwise strongly cohesive O–H O interactions. All difference spectra from the fundamental OH-stretching contours cross at the X(Z,X+Z)Y isobestic frequency of 3425 cm−1. Also, total integrated Raman intensity decreases occurring below 3425 cm−1 with temperature rise were found to be proportional to the total integrated intensity increases above 3425 cm−1, indicating conservation among the HB and NHB OH-stretching classes. From the enthalpy of vaporization of water at 0 °C, and the ΔH°1 of 2.6 kcal/mol O–H ⋅⋅⋅ O, the additional enthalpy, ΔH°2, needed for the complete separation of the NHB O–O nearest neighbors is ∼3.2 kcal/mol O–H ⋅⋅⋅ O or ∼6.4 kcal/mol H2O (13 kJ/mol O–H ⋅⋅⋅ O or 27 kJ/mol H2O). The NHB O–O nearest neighbors are held by forces other than those involving H ⋅⋅⋅ O partial covalency, i.e., electrostatic (multipole), induction, and dispersion forces. The NHB O–O pairs do not appear to produce significant intermolecular Raman intensity because they lack H ⋅⋅⋅O bond polarizability, but the corresponding NHB OH oscillators do contribute weakened Raman intensity above 3425 cm−1. An ideal solution thermodynamic treatment employing ΔH°1 =2.6 kcal/mol O–H ⋅⋅⋅ O, the HB mole fraction, and the vapor heat capacity, yielded a very satisfactory specific heat value of 1.1 cal deg−1 g−1 H2O at 0 °C. The NHB mole fraction, fu, from the YW treatment is negligibly small, 0.06 or less, for t<−50 °C. However, fu increases to 0.16 at 0 °C, and fu≊1 at 1437 °C, where recent shock-wave Raman measurements indicate loss of all partially covalent, charge transfer hydrogen bonding.

Thermal Monitoring: Raman Spectrometer System for Remote Measurement of Cellular Temperature on a Microscopic Scale

“…The isosbestic point refers to the wavenumber at which spectra taken at different conditions (e.g., temperatures, pressures, and potentials) cross putatively due to the equilibrium between the hydrogenbonded and nonhydrogen-bonded hydroxyl species [19], [20]. The isosbestic point value is this study is well within the determined 3,400-3,500 cm À1 range for the liquid water under different polarization conditions [9], [19].…”

“…Possible vibrational modes include symmetric stretching (m 1 ), an overtone of bending (2m 2 ), and antisymmetric stretching (m 3 ) [6], but experimental studies indicate that only the m 1 mode is prominent in the Raman measurements [7], [8]. The width and multipeak shape of the m 1 mode has been attributed to coupling of the hydroxyl group stretching with the energy of intra-and intermolecular hydrogen bonds [6], [9]- [11]. Formation of these hydrogen bonds can reduce the wavenumber [7] and amplitude [12] of this hydroxyl stretching motion.…”

Optical Kerr effect of liquid and supercooled water: The experimental and data analysis perspective

“…These correspond to the two broad bands centered at about 50 cm −1 and 200 cm −1 , generally addressed in the literature [23][24][25][26] as "bending" and "stretching" modes of the hydrogen-bond network, respectively. At long times the signal shows a monotonic decay; in the first OKE investigations it was interpreted as a bi-exponential relaxation, due to single molecule orientational dynamics 27 .…”

Application of Integral Equation Joined with the Chain Association Theory to Study Molecular Association in Sub- and Supercritical Water

“…26 In the present work, the complete set of the parameters for the effective Kihara potential function (eqs 27-29) have been used for the RDF calculations of water molecules by the integral equation method and the constants of these parameters have been evaluated.…”