Understanding water structure from Raman spectra of isotopic substitution H₂O/D₂O up to 573 K

Abstract

The OH/OD stretch band on Raman spectra of water is complex, and understanding the spectral features based on water structure needs further study. This study investigates Raman spectra of isotopic substitution (IS) of water (with volume ratio V/V of 0/1, 1/4, 1/1, 4/1 and 1/0) at temperatures from 303 to 573 K. The data show that the OH and OD stretch band profiles are similar in their dependences on temperature and IS ratio. IS reduces the band widths at low temperatures but the reducing effect diminishes above ∼450 K, due to the largely enhanced intensity of the high-frequency shoulder (∼3650 cm/2690 cm), which turns into the main peak for the OH (or OD) stretch bands when V/V (or V/V) reaches 1/4 at temperatures over ∼510 K. These spectral features strongly indicate a multi-structure model stating that water has various local hydrogen bonding (HB) environments. Intermolecular vibrational couplings are important in determining the band width, while intramolecular vibrational couplings are not recommended for interpreting the OH/OD stretch band. Five dominant HB configurations are identified in water: two types of tetrahedral, single donor (SD) HB configuration, single hydrogen-bonded water (SHW), and free water (FW) without any hydrogen bonds, which are represented by five sub-bands. It is estimated that most (>50%) of the water molecules are in highly asymmetric HB environments (SD and SHW). The increase of temperature breaks HB structure and IS further promotes structure transition from tetrahedral to SD, SHW and FW. Then, number of hydrogen bonds in water are greatly reduced by temperature and IS.

Effect of Hydrogen Bonding on the Surface Tension Properties of Binary Mixture (Acetone-Water) by Raman Spectroscopy

“…At the same time, the vibration force constant becomes small. The molecular structure in pure water is divided into three categories: free water molecule, partially hydrogen-bonded water structure in which hydrogen bond with one or more surrounding molecules was formed, and a tetrahedral hydrogen-bonded structure in which hydrogen bonding with one and three surrounding water molecules are connected [28,29]. The vibrational band of the OH bond is considered as the characteristic band of H 2 O.…”

“…It can avoid direct interaction with molecules and molecular structure, especially useful for of structure and weak interactions of aqueous systems, which was different from other high-energy ion testing. It was a better way to understand aqueous solutions [22,28,29]. So far, despite the fact that a lot of work has been done on aqueous solutions by Raman spectroscopy, the diversity of the situations investigated has led to various interpretations and/or controversial discussions on the structure of water.…”

“…So far, despite the fact that a lot of work has been done on aqueous solutions by Raman spectroscopy, the diversity of the situations investigated has led to various interpretations and/or controversial discussions on the structure of water. [27][28][29][30][31]. The important breakthrough of water structure was proposed by the Raman vibration peak of OH-bond, as a signal region [22,28,30,[32][33][34].…”

Robust and rapidly tunable light source for SRS/CARS microscopy with low-intensity noise

“…The resulting spectrum clearly resolves the stretching vibrations of OH and OD at 3425 and 2500 cm −1 . From spontaneous Raman measurements, 24 it is known that both bands should exhibit weak shoulders at 3650 / 3250 and 2690∕2395 cm −1 , which can already be discerned from this spectrally coarse scan. Finally, the ratio of the Raman signal between OD and OH band matches the expectations from the literature.…”

“…Finally, the ratio of the Raman signal between OD and OH band matches the expectations from the literature. 24 To judge the accuracy of the retrievable Raman response, the spectrum of pure acetone has been measured and is compared to a spontaneous Raman signal in Fig. 4(b).…”